National Institute of Standards and Technology 

Gaithersburg MD 

f.martzloff@ieee.org 

Reprinted, with permission, from IEEE Transactions on Industry Applications IA-26, March/April 1990 

First presented at the IEEE-IAS Annual Meeting, Pittsburgh, 1989

Significance: 

Part 4 – Propagation and coupling of surges 

The paper reports a rare opportunity for injecting surges in a full-size building, before and after it became populated with 

manufacturing and information technology equipment. The surges, of the unidirectional type or the ring-wave type 

described In ANSI/IEEE Standard C62.41-1980, were injected at one point of the system and the resulting surges 

arriving at other points were measured. 

The results show how unidirectional surges couple through transformers and can produce a ring wave component in the 

response of the system. Once again, it was observed that even in this relatively large building, a 40-m long branch circuit 

produces the transmission line reflection effect of an open-ended line only on the front part of the 0.5 μs – 100 kHz ring 

wave. (At 200 m/μs propagation speed, the travel time for a 40-m long line is only 0.2 μs.) 

Limited tests on the injection of the 5/50 ns EFT burst verified again the loss of steepness in the front of a nominal 5 ns 

arriving as a 100 ns front after traveling along 95 m of branch circuits. (See pdf files “Propagation EFT1 1987” and 

“Propagation EFT2 1990” in this Part 4.) 

An unexpected side effect of these surges, applied to the power lines only, was the apparent damage suffered by the 

data line input components of some computer-driven printers. That particular finding became significant in developing 

the concept of “surge reference equalizers “ – a surge protective device through which both power wires and data wire 

are routed, also more recently known as “multi-port surge protector.” 

Filename: Propagation 1990
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 26, NO. 2, MARCHIAPRIL 1990 193 

oupling . , Propagation, and Side Effects of Surges 

Industrial Building Wiring System 

Abstract-Measurements were made in an industrial building to 

determine the propagation characteristics of surges in the ac power wiring 

of the facility. The surges, of the unidirectional type or the ring-wave type 

described in ANSWIEEE Standard C62.41-1980, were injected at one 

point of the system and the resulting surges arriving at other points were 

measured. The results show how unidirectional surges couple through 

transformers and produce a ring wave component in the response of the 

system. An unexpected side effect of these surges, applied to the power 

lines only, was the apparent damage suffered by the data line input 

components of some computer-drivep printers. 

P REVIOUS MEASUREMENTS have been reported on the 

propagation of surges in the lines used for industrial and 

residential power systems. These measurements were made in 

the laboratory on a point-to-point line, isolated from the 

building wiring system or grounds. These measurements 

indicate little attenuation of slow-front surges as they propagate along the line [I], [2]. In contrast, the propagation of the 

fast-front surges follows the behavior expected from classical 

transmission line analysis [3]-[5]. For fast-front surges, the 

amplitude changes at interfaces where an impedance mismatch 

exists. The difference between slow and fast is relative and is 

only a way to relate the duration of the surge rise time to the 

travel time of the surge along the line. In the wiring of an 

actual building, the configuration is more complex, involving 

multiple branch circuits, transformers, and changing loads. 

An opportunity arose to perform new surge propagation 

measurements during two stages of a new building project: 

before any loads were connected, and after the owner had 

moved in and various loads had been installed in the building. 

Surges representative of the types encountered in low-voltage 

power circuits were injected at various points of the wiring 

system. The resulting surges appearing at other points of the 

system were measured and synchronized with the injected 

surges by several disturbance monitors, in conjunction with 

two storage oscilloscopes. The results of these measurements 

give new insights on the coupling of surges into other parts of 

the wiring system not directly connected to the part being 

surged, as well as on their propagation along the various 

branch circuits in the building. Some of the more important 

Paper IPCSD 88-24, approved by the Power Systems Engineering 

Committee of the IEEE Industry Applications Society for presentation at the 

1988 Industry Applications Society Annual Meting, Pittsburgh, PA, October 

2-7. Manuscript released for publication May 11, 1989. 

The author is with the National Institute of Standards and Technology, 

Building 220, Room B344, Gaithersburg, MD 20899. 

IEEE Log Number 8932121. 

I ( MAIN SERVICE 

480 L-L/277 L-N 1150 kVA 

I I I I I 

I I I I I 

191 191 El la m PANEL L PANEL HVAC PANEL 1 PANEL 2 PANEL 3 

LEGEND 

Tl - 480A/208A-l20Y 75 kVA - -40 m CONDUIT LENGTH 

T2 - 4BOA /208A -120Y 75 kVA 40 

T3 - 4BOA /208A -120Y 45 kVA - NUMBER OF BRANCH CIRCUITS 

Fig. 1. Simplified one-line diagram of building power wiring. 

findings will be described: 

coupling of the surges through the system stepdown 

transformers; 

conversion of unidirectional surges into oscillatory 

surges; 

propagation of the surges in branch circuits; 

difference in the propagation of fast-front versus slowfront surges; 

(these four types of measurements were the intended prime 

objective); and 

measurement of the coupling into adjacent but not 

connected wiring; 

anecdotal discussion of component failures in data ports 

of printers during surge tests on the power lines. 

EXPERIMENTAL PROCEDURE 

Building Power System 

Fig. 1 shows a simplified one-line schematic of the 

building power system. Three-phase service is provided at the 

4801277-V level by a step-down transformer outside the 

building. A 4801277-V bus provides power directly to a 

lighting panel and a heating-ventilation-air-conditioning 

panel. Other loads in the building are supplied at 2081120 V 

through three transformers, each with a distribution panel 

feeding the individual branch circuits. Special efforts were 

0093-9994/9010300-0193$01.00 O 1990 IEEE 
194 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS. VOL. 26. NO. 2. MARCHIAPRIL 1990 

SURGE GENERATOR 

h 

A 

A 

208/120 V 

AUTO-RANGING MONITOR 

Fig. 2. Coupling of surge through delta-wye step-down transformer. 

made during the construction to record the actual length of the 

branch circuits for accurate documentation of the system. 

Surges were injected and measured at various points on the 

system that were accessible at the panels or at the end of 

branch circuits. The resulting surges arriving at other points of 

the system were measured simultaneously with, the injected 

surge, to characterize the propagation of the surges. These 

points of injection (sending end) and arrival (receiving end) 

are shown by the numbers in parentheses in Fig. 1. The length 

of conduit between the panel and the end of the branch circuit 

is also shown in the figure. These numbers will be used in 

describing the various configurations of the tests reported in 

this paper. 

Instrumentation 

Three types of instruments were used in the tests: 

a surge generator capable of delivering either the 1.2150- 

8120-ps combined surge or the 100-kHz ring wave, as 

described in 161, [7] ; 

storage oscilloscopes for monitoring the surge at the 

sending end and at the receiving end; 

disturbance monitors with auto-ranging and graphic 

output capability. 

A complete description of the instruments and the surge 

coupling method is given in the Appendix, together with some 

practical suggestions on making field tests. 

Test Schedule 

Widely varying configurations were explored; those reported here are the most illustrative of the propagation 

characteristics of typical surges in this typical installation. The 

tests were performed in two phases: first when the building 

was unoccupied, so that a no-load condition existed; and 

second, with the building operational and under representative 

loading conditions. Two types of surges were applied: 

a 1.2150-ps unidirectional surge representative of a 

conventional lightning surge, applied to the service 

entrance and impacting the whole building; 

a 100-kHz ring wave representative of a conventional 

switching surge, applied at some point of the building and 

propagating in the system, for each of various combinations of the connected loads. 

MEASUREMENT RESULTS 

Unidirectional Surge Propagation 

The unidirectional 1.2150-ps surge is generally considered 

representative of lightning surges on the incoming service 

entrance 161, [8]. A scenario equivalent to having such a surge 

impinge on the building was created by injecting the surge at 

an accessible point (I) of the lightning panel L in Fig. 1. From 

that point, the surge propagated to the 480-V bus, through the 

4801208 V transformers, to the distribution panels and the 

branch circuits. In a first set of measurements, the surge 

arriving at point (2) of the panel fed by transformer T1 was 

recorded for a surge injected at point (1). These measurements 

were made at the initial stage, in the empty building, before 

any of the load equipment was connected. 

The surge was injected between two lines on the primary 

side and coupled to the corresponding line-to-neutral pair of 

lines on the secondary side of the 4801208-V delta-wye 

transformer (Fig. 2). To find which of the three secondary 

phases is coupled to the primary phase of surge injection, the 

auto-ranging disturbance monitor was connected to all three 

phases on the secondary side. 

Fig. 3 shows the graphic display obtained with that 

instrument. Phase B has the highest amplitude and thus 

corresponds to the direct coupling on one leg of the transformer. Phases A and C correspond to the coupling by the two 

other legs of the transformer, effectively connected in series 

on the delta-coupled primary side. Note how the auto-ranging 

feature of the instrument changes the time scale of the graphics 

to display a longer time sweep for phase B, where the 

disturbance remains high for a longer time than for the smaller 

disturbances on phase A and C. The direct coupling path 

having been identified, the storage oscilloscope used for the 

recordings of Figs. 4-7 was then connected across phase B. 

One probe was connected to the line conductor, the other to 

the neutral conductor. A differential connection was thus 

obtained, according to the recommended practice for surge 

measurements [9]. 

Figs. 4 and 5 show the recordings for a circuit condition 

with minimum wiring connected to the 480-V bus. Only 

breakers at points (I) and (2) in Fig. 1 are closed on panels 

L and 1. Transformers TI, T2, and T3 have their primaries 

connected to the 480-V bus, but their secondaries are 

connected only to input lugs of the distribution panels. With 

the main service circuit breaker open, the utility connection is 

severed. 

In Fig. 4, a 600-V 1 .2/50-ps surge is generated and injected 

at point (1) (Fig. 1). In this configuration, the connection from 

the lighting panel is used as an equivalent to the service 

entrance connection for bringing the surge to the 480-V bus. 

Fig. 4(a) shows the open-circuit voltage of the surge generator 

before connection to the sending end point (1). Fig. 4(b) shows 

the voltage recorded at point (I), indicating interaction 

between the surge generator and the circuit under test. Fig. 

4(c) shows the voltage recorded at the receiving end point (2), 

where the unidirectional surge has acquired an oscillatory 

component. This conversion of a unidirectional surge into an 

offset oscillatory wave illustrates the basis for introducing the 

concept of ring waves into [6]. 
MARTZLOFF: SURGES IN INDUSTRIAL WIRING SYSTEM 

I- IL A 

I LO 111 I- m c E IN . 0 = I n .-0 

I - ea I* .. -~m I E: n VI--LO 

I "7 04 I -. a I v, r- I WVI I w-- I1I I **LO I m= - 4 WLV3 

I 1L (Uo I 0 UI-7 I W >ZaE I> (0 

IU A N mm ILL:~Q. .m I L, a0 1W E 1.2 - I - I m IW la I Y I1J 3 IW 

I0 Z 

~n I n u 

-1608U1 ' "' '' '' '' I 880 U/diu uertical 12.8 us/diu horiz. 

. . . . 

......... 125.8 U/diu uertical 12.5 ms/div horiz. 

R NEUT IMPULSE 

335 LRKESIDE RCU Mar 21 1987 5:53 PH 

1688U '"" '' 

880 U/d~v vertical 182.4 usldiv horiz. 

........ 

......... 125.8 U/diu uertical 12.5 rs/div horiz. 

B NEUT IMPULSE 

335 LUKESIDE RCU May 21 1987 5:53 Pti 

-1608UL ' "' " " " I 888 U/diu uertical 51.2 us/div horiz. 

125.0 

...... Uldiu uertical 12.5 I 

ms/div horiz. 

C NEUT IMPULSE 

335 LUKESIDE RCU Hay 21 1987 5:53 PM 

Fig. 3. Graphic display of surges on three phases at receiving end (2). Note highest impulse on phase B, indicating direct coupling, 

and auto-ranging of two sweep rates. 

Fig. 5 shows the recordings at the sending end and at the 

receiving end for an open-circuit voltage setting of 3000 V by 

the surge generator. A comparison of Figs. 4 and 5 yields 

interesting results. First, on a qualitative basis, the voltage at 

the receiving end in both cases contains a unidirectional 

component with superimposed oscillation. A line has been 

marked on the oscillograrns to show the unidirectional 

component at the center of the oscillation. 

Second, quantitative inspection of the results yields further 

insight into the coupling of the surge through the transformer. 

For the 600-V sending-end condition (Fig. 4), the resulting 

unidirectional component is 150 V, or a 4: 1 ratio, which is 

precisely the 4801120 turns ratio of the step-down transformer. 

For the 3000-V sending-end condition (Fig. 5), the unidirectional component is 750 V, again a 4: 1 ratio. This constant 

ratio demonstrates the linearity of the transformer in coupling 

unidirectional surges over a 5: 1 range of overvoltages. 

The response of the combined transformers TI, T2, and T3, 

and the 480-V bus is a 370-kHz ringing overshoot, peaking, 

respectively, at 380 V (Fig. 4) and at 1900 V (Fig. 5). The 

corresponding overshoot ratios are 3801150 = 2.53 and 

19001750 = 2.53, again showing the linearity of the response. 

Thus tests for propagation only (no nonlinear protective 

devices in the system) could be performed at low surge 
Fig. 4. Recordings at sending end (1) and receiving end (2). for 600-V 

unidirectional surge. Minimum wiring connected 480-V bus (breakers to 

277 V branch circuits and 120 V branch circuits open). Voltage: 100 Vldiv; 

sweep: 2 psldiv. (a) Open-circuit output of surge generator. (b) Voltage at 

sending end. (c) Voltage at receiving end. Note line showing unidirectional 

component. 

voltages and produce valid results for higher surges. However, interest in evaluating the effects of surge-protective 

devices was a motive for making further tests with relatively 

higher surge levels. This paper, however, is primarily 

concerned with the propagation aspects. Surge-protective 

devices will by fully discussed in a later paper. 

Figs. 6 and 7 show the recordings, for the same injected 

unidirectional surge, when more of the wiring system is 

connected to the circuit under test, with the system still 

isolated from the utility supply. In the test illustrated by Fig. 6, 

lighting circuits were connected. Although the fluorescent 

lights were not operating, the built-in capacitors of the ballasts 

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 26, NO. 2, MARCHIAPRlL 1990 

(b) 

Fig. 5. Recordings at sending end (1) and receiving end (2), for 3-kV 

unidirectional surge. Minimum wiring connected 480-V bus (all breakers to 

277 V branch circuits and 120 V branch circuits open). Voltage: 500 Vldiv; 

sweep: 2 psldiv. (a) Voltage at sending end. (b) Voltage at receiving end. 

Note line showing unidirectional component. 

(a) - i_ii---~- 

~~ : t . 26 , : t I .*,, 1 i 

,,*, 

, - . . . - - . . . . . . . . - . . ,+.. 

1.i .... :. . 

. . . . -. . ..* 

(b) 

Fig. 6. Recordings at sending end (1) and receiving end (2), for 3-kV 

unidirectional surge. All 277-V lighting branch circuits connected to 480-V 

bus. Voltage: 500 Vldiv; sweep 2 psldiv. (a) Voltage at sending end. (b) 

Voltage at receiving end. Note line showing unidirectional component. 
MARTZLOFF: SURGES IN INDUSTRIAL WIRING SYSTEM 

(b) 

Fig. 7. Recordings at sending end (1) and receiving end (2), for 3-kV 

unidirectional surge. All 120-V branch circuits connected to 480-V bus 

through three 4801208-120-V step-down transformers. Voltage: 500 Vldiv; 

sweep 2 psldiv. (a) Voltage at sending end. (b) Voltage at receiving end. 

were effectively added to the circuit. At the receiving end, a 

unidirectional component of 700 V with a 150-kHz ringing 

overshoot with a ratio of about 1.25 can be observed. 

In the test illustrated by Fig. 7, all of the circuit breakers at 

panels 1, 2, and 3 of Fig. 1 were closed, adding the 

corresponding branch circuits, but without loads at the 

receptacles. The response at the receiving-end, point (2) in 

Fig. 1, still shows a unidirectional component of 700 V, but 

the ringing overshoot is now quickly damped out. 

These three circuit conditions illustrate the wide range of 

ring waves that occur when a wiring system is stimulated by a 

unidirectional surge. The general prevalence of ring waves in 

building wiring systems was confirmed by these initial tests, 

so that most of the other tests were made with the 100-kHz 

ring wave. 

Ring- Wave Surge Propagation 

Further measurements were made with the ring waves 

injected at the sending-end, point (3) in Fig. 1. Amving surges 

were recorded at the receiving-end, point (4). This scenario 

corresponds to a surge being generated by some equipment 

within the building, or the surge resulting from system 

stimulation by lightning. A few measurements were also made 

to investigate propagation from point (3) to point (5), to 

illustrate coupling through two cascaded wye-delta and deltawye transformers, but these did not produce remarkable 

results. 

The ring wave used for these measurements is defined in 

[7]; Fig. 8 shows the open-circuit voltage of a generator 

Fig. 8. 0.5 ps-100 Wz ring wave defined in [6]. 

producing such a wave. The use of a 100-kHz ring wave with a 

0.5-ps rise time for the tests introduces an additional parameter: the reflections at the ends of the lines become significant 

for the lengths of some branch circuits found in this building. 

For a velocity of propagation on the order of 200 mlps, a 

length of line greater than 50 m means a travel time longer 

than the rise time of the surge, so that reflections become 

significant [2]. 

The measurements covered a series of tests; the propagation 

path between the sending and receiving ends was progressively modified. Starting with simple point-to-point configurations, branch circuits were added by closing all breakers at 

Panel 1, connecting the secondary of transformer TI, and 

terminating the line at point (4) with various loads. 

Figs. 9, 10, and 11 show typical recordings for three of 

these configurations. Fig. 13 will present a summary of the 

various configurations with resulting propagation characteristics for the ring wave, after first discussing in detail the 

features of the three recordings of Figs. 9-1 1. 

Simple Line from Point lo Point 

For the case of Fig. 9, no breakers other than 2, 3, and 4 are 

closed at Panel 1 ; the configuration is a simple point-to-point 

line from point (3) to (4). Fig. 9(a) is the recording at the 

sending end, located 40 m from Panel 1. The waveform shows 

the interaction occurring between the surge generator and the 

wiring system. Fig. 9(b) shows the recording at intermediate 

point (2) and presents some interesting features, as follows. 

1) The initial peak of 1100 V at the sending end has been 

attenuated to 750 V, a ratio of 0.68, after 40 m of travel from 

point (3) to point (2). 

2) A second peak is visible, about 0.6 ps after the first: the 

pulse arriving at the open end of point (4) is reflected with 

twice the amplitude and travels back toward Panel 1. It amves 

at Panel 1 after a 2 x 55-m travel, requiring about 0.6 ps for 

the round trip at a velocity of 200 mlps; this expected time 

matches the time observed between the two peaks. 

3) The returned pulse, arriving at Panel 1 after 110 m 

round-trip travel in the line, has lost some its higher frequency 

components [3] and is less sharp than that coming from the 

sending point. 

4) The returned pulse travels further back to sending point 

(2), where it arrives to produce a discontinuity in the trace 

visible at the first zero crossing of the trace in Fig. 9(a). 
198 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 26, NO. 2, MARCHIAPRIL 1990 

Fig. 9. Recordings at sending end (3), intermediate point (2) of Panel 1, and 

receiving end (4) for 100-kHz ring wave and point-to-point propagation in 

simple line. No additional branch circuits have been connected between 

points (3) and (4). Voltage: 500 Vldiv; sweep: 2 psldiv. (a) Voltage at 

sending end. (b) Voltage at Panel 1. (b) Voltage at receiving end. 

5) The second peak of the ring wave (negative peak) and the 

third peak (positive peak) do not show very significant changes 

in amplitude among the three oscillograms. These peaks do not 

contain the high-frequency components associated with the 

initial fast rise, and thus are not significantly attenuated by the 

40- or 95-m travel along the line. 

Finally, Fig. 9(c) shows the initial peak, which traveled 

95 m from the point of origin and, therefore, might be 

expected to have been attenuated about twice as much as 

between points (3) and (2), a 40-m travel. (The attenuation is 

not quite proportional to distance, as the higher frequency 

components suffer greater attenuation in the early parts of the 

(c) 

Fig. 10. Recordings at sending end (3), intermediate point (2) of Panel 1, 

and receiving end (4) for 100-kHz ring wave. Transformer T1 is connected 

at Panel 1 and supplies power to branch circuits 3 and 4. Voltage: 500 VI 

div; sweep 2 psldiv. (a) Voltage at sending end. (b) Voltage at Panel 1. (c) 

Voltage at receiving end. 

travel; the waveform contains fewer of them, and is therefore 

less attenuated in the end parts of the travel [4] .) The expected 

amplitude of the attenuated pulse arriving at point (4) should 

be about 1100 V, the initial value, attenuated by about two 

times (twice the distance) the 0.68-ratio noted between points 

(3) and (2): 1100 x 0.6g2 = 5 10. The oscillogram shows, on 

the contrary, a 1050-V peak, or close to twice the expected 

arriving pulse value-the doubling effect at the open-ended 

transmission line. 

To summarize the observations from Fig. 9 data, the first 

peak, with a duration shorter than the travel time in the line, 

exhibits all the behavior of pulses traveling in a transmission 

line. Later peaks, with durations longer than the travel time, 
MARTZLOFF: SURGES IN INDUSTRIAL WIRING SYSTEM 

:w -T: 

.-.* -+-. -. .. 84,. 

Fig. 11. Recording at receiving end point (4) for 100-kHz ring 

wave. Transformer T1 is connected at Panel 1 and supplies power to all 

loads connected to branch circuits of that panel. Voltage: 100 V/div; 

sweep: 2 psldiv. 

exhibit little attenuation for the 40- and 95-m travel distances 

in this building. 

Adding Complexity to the System 

Fig. 10 shows the recordings at the same three points 

discussed for Fig. 9 but with transformer T1 connected to 

Panel 1 and supplying power to that panel. All other branch 

circuits of that panel are still left disconnected. 

Fig. 10(a) shows the sending end to be little different from 

Fig. 9(a), except that later reflections have modified subsequent peaks. Fig. 10(b) shows again the double peak at Panel 

1, resulting from the initial pulse arriving from the sending 

end, followed by a reflected pulse coming back from the 

receiving end. Fig. 10(c) shows the initial pulse arriving at the 

receiving end, doubled by the effect of the open-ended line in 

the same manner as discussed for Fig. 9(c). The same 

conclusions as those drawn from Fig. 9 apply here: the initial 

peak behaves as a pulse in a transmission line, and subsequent 

peaks are not significantly attenuated. The inspection of 

subsequent peaks is no longer as simple as it was for Fig. 9, 

because with the added elements in the transmission path, the 

cumulative effect of the reflections distorts these peaks. 

One further stage in the reconstitution of the building wiring 

system is illustrated by Fig. 1 I, where all branch circuits at 

Panel 1 are now connected, supplying their normal loads with 

power obtained from transformer TI, which is energized. For 

the same ring wave of 1100 V applied at the sending end, point 

(3) in Fig. 1, the first peak at the receiving end, point (4), is 

only 220 V, down from the 1000 V of Fig. 10. This large drop 

is caused by the impedance mismatch resulting from connecting the many parallel transmission lines at Panel 1. Even the 

subsequent peaks show a reduction (down to 100 V from the 

400 V of Fig. lo), but the waveform is so distorted by the 

cumulative effect of the multiple reflections that a simple 

analysis by inspection is no longer possible. Computer 

modeling might be an interesting task for specific cases where 

a rigorous prediction would be of interest [lo], [I I]. 

Summarizing now all the observations from the ring-wave 

measurements, three major conclusions emerge. 

1) In a building with no or few loads, fast-front surges 

propagate in a manner that can be readily predicted by 

classical transmission line analysis. 

1 

4 1(U _1-- 

Fig 12 Recording at recelvlng end pomt (4) for fast-front surge, lnjected at 

sendlng end (3) by generator with 5 ns nom~nal rise tune. 

2) Adding many parallel branch circuits produces amplitude 

reductions, predictable by the impedance mismatch at the 

point of parallel connections. 

3) Surges having durations longer than the travel time 

within the building propagate with very little attenuation for a 

relatively simple configuration. In a building of complex 

configuration, cumulative effects of reflections from branch 

circuits with random lengths tend to reduce subsequent peaks 

by averaging out their interaction. This observation, however, 

leaves open the possibility of a random combination that could 

enhance subsequent peaks, or at least not reduce them by the 

averaging effect. 

Propagation of Fast Transients 

The unplanned availability of a surge generator having a 

rise time of a few nanoseconds made possible incidental tests 

of the propagation of fast transients in the building. However, 

suitable probes were not available to record accurately the fast 

rise time at the sending end. Only the receiving-end surges 

could be observed with confidence, because the rise time 

observed there was indeed longer than the response time of the 

probes. For a nominal 5-ns rise time available at the generator 

output and injected at the sending end, point (3), the rise time 

observed at the receiving end, point (4), was 100 ns (Fig. 12). 

This increase in rise time confirms the findings reported 

earlier in [4] and 151. This observation also confirms that 

concerns over the presence of surges with rise times of a few 

nanoseconds are not generally applicable to power systems for 

locations remote from the source of the fast transients [12]. 

Summary of Ring Wave Propagation 

Fig. 13 presents a summary of the attenuation observed for 

various configurations of the building wiring. The many 

values obtained show how difficult a prediction would be for a 

complex system, but such data are helpful in providing some 

upper and lower bounds. In this figure, the transmission path 

is represented by a branch circuit from the sending end (left 

line) to Panel 1 (box at center) and an emerging branch circuit 

to the receiving end (right line). 

From the top to the bottom of Fig. 13, various combinations 

of added circuits are shown at Panel 1 and at the receiving end, 

labeled A through K. The numbers shown at the right of each 

configuration, A through K, are the observed values at the 

receiving end. For the first column, the numbers are the value 
200 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 26, NO. 2, MARCHIAPRIL 1990 

SENDING END 

RING WAVE 

(100%) 

RECEIVING END 

PERCENTAGES 

FIRST THIRD 

PEAK PEAK 

I I 

I I 

A 1.9 NSR 

---- jb ---, I I 

-0 

I 

1.7 NSR 

1000 OHMS 

100 OHMS f 0-0 95 100 

T 

(FIGURE 9) 

70 

NSR 

75 

65 NSR 

H - 90 90 

(,IGURE lo' 2 I 2.5 15 

(FIGURE 111 

2 

"P? 

NSR 

LEGENO: 

v, - POWER SUPPLY ON x NSR - NO SIMPLE 

-TRANSFORMER Ti READING 

rrm CONNECTED POSSIBLE 

'-1 BRANCH CIRCUITS 

CONNECTED 

Fig. 13. Schematic representation of configurations for propagation path 

from sending end (3) to receiving end (4). Numbers at right are receivingend percentages of first and third peaks of arriving surges for ring wave of 

100 percent applied at sending end. 

of the first peak; for the second column, the numbers are the 

value of the third peak (second positive peak of the ring wave). 

These numbers are given as percentages of the sending-end 

values of the first peak. In some cases, the response of the 

circuit was so complex that no simple reading could be made at 

the time of the third peak, hence the entry "NSR" in the 

second column. 

Configurations A, B, and C show all breakers open at Panel 

1, so that no direct metallic connection exists between the 

sending and receiving ends. However, the proximity of the 

wires in common conduits shared for part of the distance is 

sufficient to couple some of the surge by the stray capacitance. 

Adding load at the receiving end between the line and the 

neutral (configurations B and C) provides a measure of the 

transfer impedance of that coupling. 

Configurations D to G show increasing complexity in the 

transmission path, with added branch circuits at Panel 1 E, 

added transformer F, and both added G, but still no power 

applied to the primary of the transformer. For configurations 

H to K, the transformer primary is energized, supplying 

power to Panel 1 and its loads. In H, only the transformer is 

connected; in I the branch circuits have been added. In J and 

K, two different types of loads have been connected at the 

receiving end, between line and neutral, to show how a lowimpedance termination reduces the reflections observed with 

higher impedance terminations. 

An unexpected side effect of the surges was found only upon 

the resumption of normal weekly operations, after the tests 

(which were performed on a weekend). Two laser printers 

shared by several personal computers and thus linked by a data 

cable had become inoperative. Repair by the service organization of the manufacturer diagnosed failed components in the 

data line port of the printer. Yet, all the surges had been 

injected into the power lines, and at levels initially deemed 

high but not hazardous to equipment designed for connection 

to typical ac power systems. 

The exact nature of the failure is unknown because the 

service organization performed repairs as a routine operation, 

not associated with this surge measurement project, and its 

repair records were not available. However, with hindsight, 

this side effect might well be explained by the following 

hypothetical, but plausible scenario. (Anecdotal information 

on problems encountered at other facilities indicates that this 

type of problem is not at all unusual. A detailed description of 

a scenario that could lead to this failure of information 

technology systems should be useful for understanding the 

problem-a first step toward avoiding it in the future.) 

Many applications of information technology equipment 

require that peripheral terminal devices (video displays, data 

entry keyboards, printers) be located at some distance from the 

computer. Frequently, terminal devices are powered by a line 

cord plugged into a wall receptacle which is on a different 

branch circuit from that of the computer. Sometimes, the 

branch circuits are supplied by different transformers (Fig. 

14). This situation produces multiple ground references and 

loops of communication cables, with the possibility of 

substantial differences in the potentials of points expected to be 

at the same zero-reference potential. 

The general practice is to have the device chassis bonded to 

the grounding conductor of the power cord. Also as a general 

practice, the zero reference of the signal circuit is bonded to 
MARTZLOFF: SURGES IN INDUSTRIAL WIRING SYSTEM 20 1 

DATA LINK 

Fig. 14. Typical arrangement for powering computer and its peripherals. 

SIGNAL LINE 

REFERENCE LINE 

6 LOGIC REFERENCES 

(cnAssrsI - 6 A - SINGLE-ENDED CIRCUIT 

SIGNAL LINES 

6- LOGIC REFERENCES 

(CHASSIS) - 6 B - DIFFERENTIAL CIRCUIT 

Fig. 15. Links between driver and receiver of computer and remote 

terminal. 

the chassis. Fig. 15 is a schematic of the receiver and driver 

circuits used to communicate between the computer and its 

terminals. This figure shows that the designer has the option of 

using single-ended transmission, where the signals are developed with respect to a zero-reference plane, or a differential 

transmission, where signals are developed as a voltage 

difference between the two signal lines. 

Typically, a twisted-pair cable or a coaxial cable is used 

between the computer and the terminal. Various types of 

shielding may be included with these cables. Intuitively, one 

might expect that the receivers and drivers linked by a shielded 

cable should be least susceptible to interference or damage. 

However, the problem encountered here does not involve 

transients coupled capacitively or inductively onto the data 

communication cables. Rather, the problem is a difference in 

the reference potentials of the chassis of the two devices, 

resulting from surges being diverted in the separate grounding 

connections of the two devices. 

Fig. 16 shows a schematic of a system consisting of a 

computer and a terminal, powered by different sources and 

linked by a shielded two-wire differential data line with zero 

reference bonded to the chassis of each device. In each power 

supply, an electromagnetic interference (EMI) filter or surge 

suppressor has been provided between the ac lines and the 

grounded chassis. 

Let us now examine the scenario unfolding when surges 

arrive on the power supply line of the computer. The 

expected role of the EM1 filter is to divert these surges to 

ground-that is, by passing the current i through the filter, 

returning it to the power source by the grounding conductor G. 

This path unavoidably has a finite inductance L. Consequently, the fast-changing current i produces a voltage drop 

L.di/dt between the computer chassis (which is the signal 

reference at the sending end) and the grounding connection of 

the power supply. At the terminal, no surge event is occurring 

at that time; the terminal chassis (which is the signal reference 

at the receiving end) stays at the potential of the grounding 

connection G' of its own power supply. The two chassis, 

therefore, the two references of the data link ports are now at 

different potentials. This difference is the L - di/dt voltage 

from the surge, plus any other voltage that might develop in 

the undefined path linking the two grounding points G and G ' . This scenario explains how surges, initially limited to the 

power lines, can impact the data port components of a system 

powered without the installation of coordinated surge suppressors on both power port and data port. 

Thus, with hindsight, this anecdote illustrates the need for 

developing and applying means of surge protection that will 

avoid the potential difference between ends of the data link. 

This need presents a challenge to the designers of an 

information technology system and an opportunity for the 

manufacturers of packaged surge-protective devices: coordinating protection of the power supply port with protection of 

the data link port in a single unit, with the same return path for 

surges diverted by the two protective devices. Such coordinated surge suppressors built for protecting both ports and 

using a single ground reference are now commercially 

available. They are sometimes referred to as "local ground 

window" [12]. 

1) The response of the step down transformer and its 

associated bus wiring to stimulation by a 1.2150-ps unidirectional surge contains two components: 

a unidirectional component matching the stimulation, and 

a ringing overshoot at a frequency dependent upon the 

circuit characteristics. 

2) The unidirectional surge couples through the transformer 

according to the turns ratio, with negligible attenuation. The 

ringing overshoot frequency depends on the circuit parameters; its peak can exceed twice the peak of the stimulus. 

3) The existence of multiple branch circuits in the building 

wiring reduces the overshoot and affects its frequency but does 

not change the unidirectional component. 

4) A ring wave with a rise time shorter than the travel time 

in a simple point-to-point line produces the expected enhancement of the surge at an open-circuit receiving end. Adding 

loads at the end of the line reduces the amplitude of the surge 

at that point in a predictable manner, according to the classical 

transmission line theory. 
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 26, NO. 2, MARCHIAPRIL 1990 

COMPUTER TERMINAL 

L ' 

N' 

G' 

r SOME ORGANIZATIONS IN-SIST ON HAVING ONE END OF THE SHIELD FLOATING 

Fig. 16. Scenario for creating difference of potential between signal references by diverting surge through grounding conductor of 

one side of the system. 

5) Adding branch circuits and other circuit elements along 

the propagation path introduces mismatches in the line 

impedance, reducing the amplitude of the initial peak of the 

surge arriving at the receiving end. Subsequent parts of the 

surges, however, are less affected. 

6) Providing protection against power line surges at the 

power line interface of devices linked by a data communication circuit does not guarantee that surges occurring in the 

power line environment will not cause damage to the devices. 

A more comprehensive protection scheme, coordinating both 

the power line and the data line, is required to ensure 

protection. 

APPENDIX 

For complete documentation of the test procedure, the 

instrumentation used in the tests is listed in this Appendix1. 

Also, some practical aspects of the procedure and logistics are 

recited here; some were planned, some resulted from hindsight. These are offered as helpful hints to anyone planning 

this type of field test. 

Instrumentation 

Surge Generator: A KeyTek Model 711 was used, with 

F3 1 coupling network and plug-in pulse waveshaping networks: P7 for 1.2150 ps unidirectional waveform, and P1 for 

100-kHz ring wave as described in [6]. 

Storage Oscilloscopes: Two Tektronix 7934 with 500- 

MHz bandwidth were used, each with pairs of matched 1000: 1 

PO15 probes or 100: 1 P6009 probes. The probes were 

connected differentially with a 7A26 vertical preamplifier 

performing the differentiation. 

Auto-ranging Monitors: A BMI 4800 Powerscope with 

three-phase multimode monitoring capability, graphic display, 

auto-ranging of sweep rate, and adjustable threshold was 

employed. 

Certain commercial instruments are identified in this paper to specify the 

experimental procedure adequately. Such identification does not imply a 

recommendation or endorsement by the National Institute of Standards and 

Technology, nor does it imply that these instruments are necessarily the best 

available for the purpose. 

Procedure 

Surge Coupling: The surges produced by the generator 

were injected into the building wiring by a 2-pF coupling 

capacitor for the initial unpowered tests. For subsequent tests 

with power on, a coupling circuit was used so that the surge 

was applied at a fixed phase of the sine wave. 

Differential Measurements: All measurements were made 

with a differential connection of two matched probes. Admittedly, the 7A13 differential preamplifier would be more 

appropriate for this type of connection, but it was not available 

for these field tests. The common-mode rejection and noise 

background were checked by connecting the two probes 

together and then to the high and low side of the point of 

measurement. 

One of the planned measurements was to measure the 

voltage between the building grounding system and one of the 

so-called "isolated separate dedicated ground" ground rods, 

deliberately installed in the building as a tutorial example of 

questionable practice. For this measurement, however, the 

differential connection with the 7A26 preamplifier and unshielded oscilloscope was not successful. The levels of 

voltages observed across the desired points of measurement 

had the same order of magnitude as the noise background 

observed in the check just described. Instrumentation less 

sensitive to this interference was not available for these field 

tests, but new attempts might be made in the future. 

While these hints might seem trivial, they are offered after 

successful planning or hindsight and as a counterpoint to the 

more fundamental conclusions of the paper. If they can save 

time or reduce problem? for future experimenters, including 

them in this paper will have been worthwhile. In random order 

of importance, here is a list. 

Whenever field measurements involve several people at 

different locations, walkie-talkies are far superior to 

direct voice communication (attenuated by distance), 

fast-footed couriers, or an internal telephone network. 

Whenever the work is carried on outside of normal 

working hours, be sure that the team includes one 
MARTZLOFF: SURGES IN INDUSTRIAL WIRING SYSTEM 

individual thoroughly familiar with the facility, and 

custodian of all keys to rooms, cabinets, and interlocks. 

The availability of monitoring instruments that combine 

logging and timing of events provides a very useful 

correlation of recordings made by independent oscilloscopes. 

Always bring at least twice as much film as you think you 

will need. The same remark applies to materials for filing 

oscillograms at the site, and to extension cords. 

Bring some spare fuse holders for the instruments. These 

protruding accessories have a unique capability of coming loose during shipment and getting lost in the packing 

material. 

When scheduling the rate of progress in the tests, 

rememb r that Murphy was an optimist! fi 

The measurements and the analysis of the results were made 

possible by the cooperation and contributions of many 

organizations and individuals, as follows: 

Building Industry Consulting Service International, for 

coordinating an informal consortium of private sector 

companies in support of this work; 

Alex McEachern, for making the facilities of Basic 

Measuring Instruments available as a measurement site; 

Joseph Connolly, Robb Gould, Jim McDaniels, and 

Christine Mihelich, for their participation in the measurements; 

Maurice Tetreault, for participating in the measurements 

and suggesting the principles underlying the analysis of 

the surge side effects on the data ports; 

Catherine Fisher, for suggestions on reporting these 

results. 

These contributions to improved understanding of the problems, and thus greater system reliability, are most gratefully 

acknowledged. 

[I] F. D. Martzloff, "The propagation and attenuation of surge voltages 

and surge currents in low-voltage ac power circuits," IEEE Trans. 

Power App. Syst., vol. PAS-102, no. 5, May 1983. 

[2] F. D. Martzloff and H. A Gauper, "Surge and high-frequency 

propagation in industrial power lines," IEEE Trans. Ind. Appl., vol. 

IA-22, no. 4, JulyIAug. 1986. 

131 L. V. Bewley, Traveling Waves on Transmission Lines. New York: 

Dover, 1963. 

[4] F. D. Martzloff and P. F. Wilson, "Fast transient tests: Trivial or 

terminal pursuit?" in Proc. Int. Zurich Symp. Electromagnetic 

Compatibility, 1987. 

[5] F. D. Martzloff and T. F. Leedy, "Electrical fast transient tests: 

applications and limitations," IEEE Trans. Ind. Appl., vol. 26, no. 1, 

pp. 151-159, Jan./Feb. 1990. 

[6] IEEE Guide on Surge Voltages in Low- Voltage AC Power Circuits, 

ANSIIIEEE Standard C62.41-1980. 

[7] R. B. Standler, "Equations for some transient overvoltage test 

waveforms," IEEE Trans. Electrornagn. Compat., vol. EMC-30, 

no. 1, Feb. 1988. 

[8] Insulation Coordination within Low-Voltage Systems, Including 

Clearances and Creepage Distances for Equipment, IEC Pub. 664- 

1980. 

191 IEEE Guide on Surge Testing for Equipment Connected to LowVoltage AC Power Circuits, ANSIIIEEE Standard C62.45-1987. 

[lo] A. K. Agrawal, H. M. Fowles, and L. D. Scott, "Experimental 

characterization of multiconductor transmission lines in inhomogenous 

media using time-domain techniques," lEEE Trans. Electromagn. 

Compat., vol. EMC-21, no. 1, Feb. 1979. 

[ll] A. H. Paxton and R. L. Gardner, "Application of transmission line 

theory to networks with a large number of component wires," in Proc. 

Int. Zurich Symp. Electromagnetic Compatibility, 1987. 

[12] F. D. Martzloff, "Protecting computer systems against power transients," IEEE Spectrum, April 1990. 

Fraqois D. Martzloff (M'56-SM'80-F'83) 

completed his undergraduate studies in France and 

received the M.S.E.E. degree from the Georgia 

Institute of Technology, Atlanta, and the M.S.I.A. 

degree from Union College, Schenectady, NY. 

After a long career at General Electric, he joined 

the staff of the National Bureau of Standards (now 

renamed National Institute of Standards and Technology) to work on conducted electromagnetic 

interference issues. His early experience covered 

high-voltage fuses, high-voltage bushings, and electronic power conversion; the latter marked a turning point to issues of 

overvoltage effects on semiconductors, surge suppression, metal oxide 

varistor applications, and interference mitigation. In addition to his research 

work on surge propagation and mitigation, he is contributing to the 

development of standards on surge environment and surge suppression within 

IEEE, ANSI, and IEC by documenting his measurements, as in the present 

paper, by presenting tutorials, and by drafting new standards.