Part 5 – Laboratory measurements 

Electronic equipment with two input ports - power and communications - can be exposed to damaging 

differences of voltage across the two ports during surge events. Two exposure scenarios of producing suc

differences of voltages are explained and illustrated by measurements performed in a replica of a residenti

or light commercial installation of power, telephone, and cable TV wiring. 

Several mitigation methods are described, and one possible retrofit solution is shown. In a later paper, (se

the pdf file “ Upsdown measure”) numerical simulations were performed on a model of the system in order 

expand the range of conditions and identify significant variables. Nevertheless, there are still very few 

published data on quantifying the stress that can be produced by these scenarios, and hopefully mitigated 

by “surge reference equalizers” -- also known as “multi-port surge protectors.” 

Filename: Upsdown surging 
Thomas S. Key and Frwois 0. Martzloff ' 

Abstraet - Electronic equipment with two input ports 

- power and communications - can be exposed to 

damaging cMferences of voltage across the two 

ports during surge events. Two exposure scenarios 

of producing such differences of voltages are 

explained and illustrated by measurements 

performed in a replica of a residential or light 

commercial installation of power. telephone, and 

cable N wiring., Several mitigation methods are 

described, and one possible retrofit solution is 

shown. It is planned that in a further phase of this 

research, numerical simulation will be performed on 

a model of the system in order to expand the range 

of conditions and identify significant variables. 

INTRODUCTION 

As more and more electronic equipment enter 

the home and business environment. these often 

invoke a communications port as well as their usual 

power cord port. In this paper, we will use the term 

'twoport appliance* or "appliance' for short. being 

understood that it covers two-port information 

technology equipment. Exampfes of such two-port 

appliances include fax machines, telephone 

answering machines, personal computers with 

modem communications or printer connections. and 

cableconnected TV receivers. Although each of the 

power and communications systems may include a 

scheme for protection against surges, the surge 

current flowing in the surged system causes a shift 

in the voltage of its reference point while the other. 

non-surged system reference point remains 

unchanged. The dierence of voltage between the 

two reference points appears across the two ports 

of one appliance, or between the communications 

ports of two appliances linked by a data cable. 

Depending-on the nature of the appliance and its 

immunity. which is not often defined. this difference 

of voltage may have some upsetting or damaging 

consequences. In this paper,-we will present just 

two examples of measurements illustrating the broad 

variety of possible exposure scenarios. 

To ident-8y and quantify the significant variabl

and their effects, a representative configuration 

the circuitry in a residence (metallic cold water pip

power and grounding conductors. telephone a

coaxial cable TV wiring) has been set up in th

laboratory, according to US. practice. The circu

have been hung from the laboratory ceiling, to d

couple them from nearby metallic masses and g

them out of the way of laboratory personnel. hen

the name 'Upside-Down House' given to the proje

To evaluate the threat of impinging surges in a

actual installation. surges of various types, 

defined in standards covering AC power circuits a

communications, can be injected at various poin

of the Upside-Down House circuits. Combinatio

of surgeprotective devices (SPDs) can also b

placed at various locations of the Upside-Dow

House. corresponding to a variety of real-wo

exposure scenarios. A measurement can then b

made of the resulting differences of voltag

appearing between the power and communicatio

ports of a single appliance. or between th

communications ports of two appliances installed 

some location within the Upside-Down House. N

conclusions are drawn in this paper on the withsta

capability of any particular appliance for this type 

threat, because the manufacturers typically do n

provide immunity data for any exposure scenario 

this type of interaction. However, some of th

voltages thus recorded in the Upside-Down Hou

confirm the suspicion derived from field failures th

damaging differences of voltages can occur. 

APPROACHES 

Various mitigation schemes have been propos

by researchers and industry. but not quantified. 

remedy upsetting or damaging voltage difference

The most effective is likely to be a fiber op

decoupling inserted in the communications link. b

the expense may be objectionable for resident

Thomas Key is with the EPRI Power Electronics Applications Center (PEAC), 10521 Research Driv

Knoxville TN 37932, USA; Franqois Martzloff is with the National Institute of Standards and Technolo

(NIST), Gaithersburg MD 20899. Contributions from NIST are not subject to copyright in the U.S.A. 

1 
offer some degree of remedy, but leaves out all 

existing installations. Increasing the appliance 

withstand capability may raise objections of market 

economics. and may not be practical for some of the 

voltages that can appear. 

Many different exposure scenarios can be 

identified. even in a simple residential circuit replica 

Reference voltage shiis are a multi-dimensional 

problem in the real world. In this paper, the problem 

has been simplified to looking at the effect of only 

twovariables: spatial relationships of conductors and 

effectiveness (including some side-effects) of SPDs. 

Other important variables that were identified but not 

addressed at this stage of the research are cited in 

the discussion section of this paper. 

In this paper, two simple exposure scenarios are 

illustrated: a voltage difference occurs between the 

ports of an appliance connected to two systems 

when a surge impinges on one of the systems, and 

a voltage difference occurs between the communications ports of two appliances powered by separate 

circuits of the same power system when a surge 

impinges on that system. In the final discussion. we 

will look into some ways of expanding these results 

and perhaps identifying a recurring set of variables - 

that can be mitigated or avoided. 

SETUP AND MEASUREMENTS 

Measurements reported in this paper describe 

exposure scenarios leading to voltage differences 

being developed during surge events across the 

power and telephone systems of the Upside-Down 

House. as well as between the signal reference 

points of two interconnected appliances linked by 

their communications ports, such as a personal 

computer (PC) and associated printer. For each 

case, the Upside-Down House circuits may include 

some form of upstream surge protection on the 

telephone service entrance or appliance port, as well 

as on the power service entrance or appIiance port. 

It is planned to continue the project with similar 

measurements involving the cable TV port. 

Figure 1 shows an isometric of the Upside-Down 

House configuration. with the arrangement of the 

three tiers of conductors shown in Figure 2. The 

power wiring includes two tiers of 3conductor cable 

(2.05 mm dia - #12 AWG, non-metallic jacket). 

~i~ure7- Schematic representation of the 

Upside-Down House conductors 

typical of residential' wiring, and one tier of thr

2.05-rnrn dia. conductors in a steel conduit, typi

of commercial or office installation. A 4conduct

two-pair telephone cable and a 704 N coax

cable also run along the 3conductor power cabl

To illustrate the expected benefit from go

wiring practice (cables routed close to the ea

reference -- the copper water pipe in the Upsi

Down House). one tier has been lashed to t

copper pipe. Of course. such idealized practice 

not practical. but will serve here as baseline a

ilbstration of EMC principles [Van Deursen. 199

In an actual installation, the system would exist in 

three dimensions. For the sake of simplification. 

Upside-Oown House has been reduced to only t

dimensions, one horizontal run spanning the hou

and the vertical separation indicated in Figure 

For the purpose of accessing both ends when inj

ting surges and measuring voltages and curren

the horizontal span has been folded into a hair

with both ends accessible in junction box JB 14

X 

Steel mnduit 

3 wnductors. bose. t12 AWG 

3 wnductors. NM jacket 2#12 +G - 

Telephone pairs 

70Ra~xcaMe 

3 wnductors. NM jacket 2#12 +G 

Telephone pairs 

70 Q coax cable 

2 conductors. bose. #12 AWG 

3/4 in. copper pipe 

X 

Figure 2 - Vertical arrangement of conducto

in the Upside-Down House (X-X of Figure 1
mediate point of the span. Short cable runs (3 m). 

not shown on the diagram. provide for appliances 

located dose to the senrice entrance. 

Neglecting the vertical separation of the three 

tiers. the length of the span from end to end is 

36 m. (This number is cited to give an idea of the 

size of the house. Any numerical computations will, 

of course, use the exact values.) A typical service 

entrance breaker panel and revenue meter have 

been provided at one end. upstream of junction box 

JB 1-4. A Network Interface Device (NID). typical of 

the U.S. practice for entry of the telephone service. 

has been instailed next to junction box JB 1-4. 

By connecting the NID grounding conductor 

(US. code terminology) to one or the other end of 

the copper pipe. it is possible to represent the 

scenario where telephone and power service enter 

at the sarne end of the house (the preferred 

practice) or at opposite ends (not preferred, but 

often encountered). All of the conductors are 

insulated from the existing earthing arrangement of 

the laboratory building. making it possible to 

represent various configurations of the earthing 

arrangement of the Upside-Down House. 

Surges were injected into the power system in 

the line-to-ground (L-G) mode. Note that the U.S. 

practice of bonding the neutral and grounding 

conductors at the service entrance makes any 

impinging L-G surge become also a line-to-neutral 

surge. Surges injected into the balanced-pair 

telephone system were in [tip & ring]-to-ground 

mode, with the NID acting to divert them to the 

common earthing point of the laboratory building and 

Upside-Down House via the copper pipe. 

The waveform and amplitude of the injected 

surges were selected to harmonize with the values 

cited in industry standards. Because of the different 

values of the impedance of the various circuits into 

which -the surges were injected. the resulting 

waveforms reflect the interaction of the surge 

generator and load impedances and do not exactly 

duplicate the familiar standard waveforms. Nevertheless. the resulting waveforms are representative 

and provide examples of the threat and needs of 

mitigation. These results will provide experimental 

data for later validation of computer modeling, so 

that the modeling can then expand the results to 

other waveforms and circuit impedances. 

TWO SYSTEMS SERVING ONE APPLIANC

In this exposure scenario, a modemequip

PC is connected by its power port to a bra

circuit. and by its modem port to the teleph

service of the house. For a worstcase scenario. 

power and telephone services enter the house 

opposite ends (Figure 3). 

Figure 3 - Power and telephone services 

entering the house at opposite ends. with P

connected across the two systems 

An open loop is formed by the copper pipe. 

protective conductor (international symbol "PF

the branch circuit f eeding the PC. and the teleph

wires from the NID to the PC. If a surge impin

on the external telephone plant, it is diverted by 

NID via the copper pipe to the common earth

point of the house, at the power service entran

The surge current in the copper pipe create

changing magnetic flux around the pipe. wh

induces a voltage in the loop. This voltage 

appear between the two PC ports if they 

separated by a high impedance (of unknown su

voltage withstand capability). 

With the telephone wires routed away from 

copper pipe -- which can be expected in reside

wiring -- a large loop is formed, embracing the 

produced by the surge current flowing in the cop

pipe. Wih the telephone wires lashed to the cop

pipe -- a theoretical more than practical routin

the loop embraces less flux and one can expe

lower induced vottage across the two ports. 

Figure 4 shows the recording obtained with 

telephone wire routed away from the pipe. Fo

rate of change in the surge current of 75 Nps

peak of 4.3 kV is induced in the loop and appe

between the two ports. For the sarne injecti.o

current. a peak of only 1.3 kV was noted with 

telephone wires lashed to the copper pipe. 
Figure 4 - Voltage difference recorded 

with telephone and power services 

entering at opposite ends of the house 

A relatively simple retrofit solution is to equalize 

the difference of vottage between the two systems 

by a device designed for the purpose and inserted 

in both communications and power links just before 

they enter the appliance. This device, defined in 

IEEE standards [IEEE Std 1 100-1 9921 as a "Surge 

Reference Equalize? is commercially available in 

the U.S. as a unit featuring a plug and receptacle for 

the power link, as well as a pair of telephone jacks 

or TV coaxial fittings for the communications link. 

However. its necessary effectiveness has not yet 

been quantified in any performance standard. 

To illustrate the effectiveness. Figure 5 shows 

the reduction of the voltage obtained by insetting a 

typical surge reference equalizer in the power and 

telephone lines at the point of connection of the PC. 

The generic design of such a device includes 

insertion in the two telephone wires of two matched 

gas tubes. two series resistors. and two silicon 

avalanche diodes. with a shared earthing reference. 

Figure 5 shows the immediate clamping effect of 

the diodes down to 200 V. followed by a further 

reduction of voRage as the gas tube sparks over. 

power service entered at the same end of 

house. the recommended practice. With su

configuration. a reduction in the voltage differen

about 75% of the large loop value was found in 

test series. Available space limits the numb

records that can be shown in this paper for va

combinations. but a more comprehensive repo

be prepared and published later. 

SECOND EXPOSURE SCENARIO: 

ONE SYSTEM SERVING TWO APPLIANCE

VIA TWO BRANCH CIRCUITS 

In this scenario. a PC and the associated p

are connected by the usual communications c

and each is powered by a separate branch ci

This situation is often encountered when a prin

shared among several users. or when an install

has been deliberately configured to provid

separation of the 'clean' branch circuit supplyin

PC from the "noisy" branch circuit supplying 

printers and other peripherals (Figure 6). 

branch circuits originate at the service panel

might not have the same length. 

In a first case of this scenario, a slight differ

may occur in the time of arrival at the two ports 

surge originating outside of the building ("EX

Figure 6). A greater difference in the time of a

would occur if the surge were internally gene

("IN") along a branch circuit. propagating direc

that branch toward the PC and in a roundabout 

via the service entrance and the other branch c

toward the printer. Wih the internally gene

surges having steeper fronts that the exter

generated surges [Mattzloff. 19901. the differen

arrival time would be significant since the vo

spike occurs upon the initial current rise. not a

..-. peak of the current surge. .... .... 

0 : Voltage between telephone pMt 

- Data link 

Figure 5 - Mitigation obtained by Figure 6 - Personal computer and printe

inserting a surge reference equalizer in . linked by a data cable and powered from 

the power and telephone lines two separate branch circuits 
devices at the power ports of the two appliances. A 

shift in the reference voltage can occur if one SPD 

provided in either the printer or the PC invites a 

disproportionate surge current in its PE conductor. 

These can be built in the appliance or be a plug-in 

device installed by the user. Such a device, if it 

includes an SPD connected L-G, will return the 

surge to the service entrance through the protective 

conductor PE ("equipment grounding conductof' is 

the US. term) and produce a shift in the voltage of 

the corresponding chassis. The resulting difference 

of voltage between the two chassis will be applied 

across the communications link with possible 

upsetting or damaging consequences. 

The effect of such difference in SPDs -is 

illustrated in Figure 7. for the worst case scenario of 

one SPD connected L-G in one appliance, and none 

in the other. An oscillatory difference of voltage 

peaking at 3.2 kV, with a spike in the nanosecond 

range. occurs at the time of the initial rise. for the 

400 Alps rate of current change corresponding to an 

8/20 ps 1400 A peak surge injected at the service 

entrance. Note the decay of the voltage to a low 

value at the time of the curmnt peak 

DISCUSSION 

The two exposure scenarios described in this 

paper represent the mechanisms most likely 

responsible for many of reported. but seldom welldocumented, field failures of two-port appliances. 

The variables considered in these two scenarios 

are marked in the cells of Table 1. (1) for the first 

scenario, (2) for the second. The columns in the 

Figure 7 - Difference of reference 

vobges caused by different protections 

in the two separate branch circuits 

table correspond to spatial variables; only a few 

all the possible variables are shown. The row

the table show a few of the possible variab

corresponding to the nature and combinations of 

SPDs. This table is a beginning toward defining 

multi-dimensional matrix of all possible variable

Many other variabtes need consideration, s

as the presence of more than two ports in 

appliances, different types of ports (serial RS2

Ethernet ...), dierent power system configurat

(single-phase 1201240 V or three-phase 120/20

in the US.. three-phase systems in other countri

wiring errors and poor practices, lack of coordina

between upstream and downstream SPDs. la

or higher buildings, separate buildings, immu

levels of equipment and consequences of insuffic

immunity (upset vs. failure, failure modes), and. 

c-. ..-. I---., --v.ovmmmmr n-uo-ur~u. uy IGVIGW 

these many variables. it may be possible to ide

a limited number of scenarios and thus de

effective mitigation means. 

Table 1 

Two-dimension matrix of variables considered for reference voltage shifts in two scenarios 

----- - --- 

Built in the appliance, or external, userprovided plug-in SPD 

r 

Spatial variables 

SPD variables 

Power service entrance SPD 

Equipment power port SPD 

Telephone service entrance SPO 

Equipment telephone port SPD ' 

Other SPD locations and types 

. . .. . . . . . 

Multiple points of 

entrance of power 8 

telephone service 

(f) 

(1) (2) 

(1 ) 

(1 

Single entrance 

of services 

("ground whdour) 

(2) 

Wiring routing 

and 

pradb 

(1) (2) 

(1 ) 

(1) (2) 

Other spatia

variables of th

installatii .
of a properly designed surge reference equalizer. 

One cause of the problem is the flow of large surge 

currents in the wiring system of the building. With a 

telephone senrice entrance located at the opposite 

end of the power sew-ke entrance. the required 

bonding of the NID unavoidably involves the surge 

current in the long bonding connection. hence the 

need for preventive mitigation for this type of nonrecommended telephone service installation, unless 

adequate betweenports immunity of the appliance 

is documented. While these examples of two such 

exposure scenarios have illustrated the mechanisms. only a computer-driven model might cover 

all possible combinations of the many variables 

that could be encountered in ail existing or future 

installations. Hence, it is essential that a comprehensive and well-documented experimental data 

base be established for validation of the model. 

For surges impinging on the power service 

entrance. the problem is associated *th large surge 

currents flowing in the branch circuits. If the surge 

current were diverted at the service entrance by a 

suitable SPD. the problem would be reducedHowever. the specification of a "suitable SPD' at the 

service entrance involves the issue of coordinating 

cascaded SPDs [Martzloff-Lai. 19921. The ongoing 

program of measurements at the Upside-Down 

House will include measurements and numerical 

simulation of cascaded SPDs. A joint Working 

Group of the IEC is developing guidelines for 

cascade coordination. based on the work of many 

-researchers [Goedde, 19901; [Standler. 19911; 

[Hostfet et at.. 19921; [Hasse et at.. 19931. 

CONCLUSIONS 

1. Quantitative measurements in the Upside-Down 

House clearly show objectionable differences in 

reference voltages- These &ur even when. or 

perhaps because. surgeprotective devices are 

present at the point of connection of appliances. 

2- Accounting for all the variables may be done in a 

multi-dimensional matrix, a task for computer 

analysis. the next step of this project. 

3. The analysis should be directed toward obtaining 

a limited set of typical scenarios resulting from 

the many combinations of many variables. 

The laboratory measurements were made w

the kind assistance of Doni Nastasi and Ke

Phipps. Glenn Grotz and Donald Worden provi

peer-review comments on the test procedure 

interpretation of the results. 

This project was made possible by a sabba

granted by NlST to Martzloff. allowing him 

experiment with his concept of the 'Upside-Do

House.' Thk Upside-Down House was installe

PEAC. with support of the Electric Power Resea

Institute. as a permanent facility of the Po

Quality Testing Network 

The authors also explicitly invite their peer

conduct similar experiments and corrputation

build a consensus on the threat represented 

shifting reference voltages. Such a consen

would be an important step toward the developm

of standards for system compatibility. 

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Goedde. G.L.. Marz. M.B., and Henry, D.C.. Coordinating 

Lightning Stroke Protedion From the UliIii System to Loa

Devices. Proceedings, Second hternational Power Quali

AS0 Conference. October 1990. Philadelphia. 

Hasse, P.. et al.. Lightning current arrester containing spa

gaps for AC supply mains. EleMrie. June 1993. 

Hostfet, O.T., et al., Coordination of surgeprotective dev

in power supply systems: Needs for secondary protedion

Proceedings, international Conference on Lghtning 

Prdedbn. Berlin. September 1992 

tEEE Std 1100.1992, IEEE Recommended Pradice for 

Powevrng and Grounding Sensitive Electronic Equipment 

CEmerald Boor of the IEEE Cdor Books series). 

Martzloff, F.D., Coupling, Propagation, and Side Effeds o

Surges in'an Mustrid Building Wiring System. IEEE 

Transactions /A-26, MdApril 1990, pp. 193-203. 

Martzloff. F.D. and Lai, J.S., Cascadiig Surge-Protective 

Devices: Coordination vs. the IEC 664 Staircase. 

Proceedings. PQ4'91 Conference. pp 191-198. 

Slandler. 4.8.. Coordination of Surge &resters and 

Suppressors for Use on Low-Voltage Mains. Proceeding

199 1 Zirrich EMG Symposium. pp 51 7-524. 

Van Deursen. A.PJ., Electromagnetic Compatibikty, Pa

Installation and MRigation Guidelines. Section 3, Cabling 

Wring, EUT Report 93-E-275, Eindhoven University of . 

Technology. July 1993.