presenting the thesis that the concept of “energy level” of a surge is inappropriate, the other presenting 

the position that monitoring surge voltages is no longer relevant. 

1. The paper offers a rationale for avoiding attempts to characterize the surge environment in low-voltage 

end-user power systems by a single number – the "energy in the surge" – derived from a simple voltage 

measurement. Numerical examples illustrate the fallacy of this concept. 

2. Furthermore, based on the proliferation of surge-protective devices in low-voltage end-user 

installations, the paper draws attention to the need for changing focus from surge voltage measurements 

to surge current measurements. This subject was addressed in several other papers presented on both 

sides of the Atlantic (See in Part 5 “Keeping up”-1995; “No joules”-1996; Make sense”-1996; “Novel 

transducer”-2000; and “Galore”-1999 in Part 2), in persistent but unsuccessful attempts to persuade 

manufacturers and users of power quality monitors, and standards-developing groups concerned with 

power quality measurements to address the fallacy of continuing to monitor surge voltages in post-1980 

power distribution systems As it turned out, the response has been polite interest but no decisive action.
SURGE RECORDINGS THAT MAKE SENSE 

Joule Deposition : Yes ! - "Joule Content" : Never ! 

Geoffrey Lindes Arshad Mansoor Franqois Martzloff David Vannoy 

Delmarva Power & Power Electronics National Institute of Delmarva Power & 

Light Company Applications Center Standards & ~echnolo~~' Light Company 

Abstract t 

This paper offers a rationale for avoiding attempts to characterize the surge environment in low-voltage 

end-user power systems by a single number -- the "energy in the surge" -- derived from a simple voltage 

measurement. Numerical examples illustrate the fallacy of this concept. Furthermore, based on the 

proliferation of surge-protective devices in low-voltage end-user installations, the paper draws attention 

to the need for changing focus from surge voltage measurements to surge current measurements. 

Introduction 

Sensible application of surge-protective devices (SPDs) requires that the capability of a candidate SPD 

be sufficient to absorb the energy that an impinging surge could deposit in the device. This eminently 

rational approach, however, was derailed when the erroneous concept was proposed that one could 

measure the "energy in the surge" and thus prescribe an easy match of the energy-handling capability of 

an SPD to the "energy" of its environment. 

In a more recent approach by standard developers, an attempt was made to express this concept as a 

"specific energy" that would normalize it with respect to a postulated resistance of a device exposed to 

the impinging surge. Our thesis is that such attempts are neither realistic nor relevant. We will show 

that these erroneous attempts, based on the classical formula for computing the energy dissipated in a 

linear load of known resistance, cannot be applied to characterize the environment. There is no 

meaningful relationship between the "energy" in a surge event as derived (erroneously) from the single 

voltage measurement and the energy actually deposited in a varistor by this surge event. 

Furthermore, the results obtained when recording surge voltages conducted since the mid-eighties have 

now become questionable as a result of the proliferation of surge-protective devices. It is very doubtful 

that a surge voltage monitor, installed in a typical end-user facility, will record anything but the residual 

voltage of unknown SPDs in the installation -- which is no measure of the threat of an incoming surge. 

Only a surge current measurement in a candidate SPD can assess the threat. 

A review of equipment failure or upset mechanisms related to the occurrence of a surge voltage reveals 

that none of these mechanisms are related to this so-called "energy in the surge." Several failure 

mechanisms other than energy-related are identified, pointing out the need to describe the surge events 

with a more comprehensive set of parameters in conducting future surveys. 

I. Electricity Division, Electronics and Electrical Engineering Laboratoty, Technology Administration, 

U.S. Department of Commerce. 

Contributionsfrom the National Institute of Standards and Technology are not subject to US. Copyright. 
The Fallacy of Joules Content 

In an attempt to characterize the potential threat of surges to voltage-sensitive equipment, recordings of 

the surge voltages occurring in low-voltage power circuits have been conducted in the last quartercentury, driven by the increasing concern about the vulnerability of new electronic appliances to 

transient overvoltages. However, practically all the recording campaigns conducted by major 

organizations such as ERA (Bull and Nethercott, 1964)', General Electric (Martzloff & Hahn, 1970)~, 

IBM (Allen & Segall, 1974)3, Bell (Goldstein and Speranza, 1982)4, Canadian Electrical Association 

(Hughes & Chan, 1995)5, National Power Laboratory (Dorr, 1995)6 and other researchers, including 

Hassler & Lagadec (1979)', Meissen (1 983)', Wernstrom et al. (1984)9, Goedbloed (1987)1°, Standler 

(1989)11, and Forti & Millanta (1990)12 have been limited to the measurement of transient voltages. 

Interest in these measurements has been re-kindled by several investigations aimed at assessing power 

quality in end-user facilities. These recordings, initially limited to measurement of peak voltages, were 

perfected with the help of increasingly sophisticated voltmeters. Early surveys were conducted with 

conventional oscilloscopes; later on, portable digital instruments with on-board computing became 

available. While these instruments made possible the recording of a voltage transient as a function of 

time and graphical presentation of data, the recording of such a surge voltage profile does not lend itself 

to a simple description by a single number. To circumvent this difficulty, many researchers called upon 

the basic concept of energy to characterize the level of surge threat in terms of voltage. Referring to 

classical electrical engineering, the instantaneous power dissipated in a resistor by a transient voltage is 

merely the square of the applied voltage, divided by the resistance. Taking the integral over the 

duration of the transient yields the energy. By analogy, the "energy" of a surge could then be computed 

from the voltage measured at some point of a power system. According to this intuitive concept -- but 

fallacious as we will show -- the greater the measured voltage, the greater the "energy" and thus the 

greater the threat to potential victim equipment. 

A review of the known failure or upset mechanisms of various types of devices and equipment identifies 

several surge parameters other than energy-related. These include source impedance, peak amplitude, 

maximum rate of rise, tail duration, and repetition rate. Thus, future surveys of surge events conducted 

with present or with even better monitoring instruments will need to include more comprehensive and 

hopefully standardized methods of presenting and interpreting the results. 

Thesis 

Our thesis is that neither the threat nor the "energy level" of a surge can be characterized by simply 

measuring the voltage change during a surge event. Any reference to the concept of "energy of a surge" 

should definitely not be introduced. Such avoidance is based on two facts: 

A voltage measurement of the surge event cannot alone predict the energy levels affecting the 

devices exposed to that surge. This is particularly true for nonlinear surge-protective devices where 

energy deposited in the device is relevant, but has little to do with the misleading concept of "energy 

in the surge" derived from an open-circuit voltage measurement. 

There are other than energy-related upset or failure modes of equipment. These effects require 

consideration of other parameters when describing a surge event to yield relevant and realistic 

assessment of surge stress threats. 

This thesis will be supported by an analysis of the impact of surges on equipment, and illustrated by numerical examples 01 varlsror appncarlons snowing now me aescriprion or a surge ~y ~ts --energycould then lead to vastly different conclusions. 

2 
Interactions Between Surges and Victim Equipment 

At this point, we need to identify the devices and equipment that may become the victims of a surge, 

and their failure mechanisms. After-the-fact investigations and experimental data show a wide range of 

surge-related upset and failure mechanisms. These include insulation breakdown, flashover, fracture, 

thermal and instantaneous peak power overloads, dvldt and dildt limits being exceeded. The following 

list gives some generic types of surge victims and the typical failure or upset mechanisms. It is highly 

significant that in all this list, the term [d x dt] or its integral does not appear. Table 1 provides a 

summary of this list of victims and relevant surge parameters associated with the failure modes. 

1. Electrical insulation, where the failure mechanism (breakdown or sparkover) is principally a 

function of the surge voltage, with the complication of a volt-time characteristic such that failure under 

impulse occurs at a level that increases when the rise time or duration of the impulse decreases. 

"Insulation" is to be taken in the broadest sense of solid or liquid material separating energized 

conductors in equipment, clearances on a printed circuit board, edges of semiconductor layers, etc. A 

distinction must be made between the initial breakdown of insulation, related to voltage only, and the 

final appearance of the damaged insulation, related to the total energy dissipated in the breakdown path. 

In another situation, the insulation of the first turns of a winding may be subjected to higher stress than 

the others as the result of the uneven voltage distribution resulting from a steep front rather than only 

the peak value of the surge. 

2. Surge-protective devices, for which the voltage across the device is essentially constant, and the 

energy deposited is a function of the surge current level and duration. One failure mode of such a device 

will occur when the energy deposited in the bulk material raises the temperature above some critical 

level. Failure modes associated with the current level, such as flashover on the sides of a varistor disc, 

failure at the boundary layers of the varistor grains, or fracture of large discs, have also been identified 

and are not directly related to energy. 

3. Semiconductor devices, such as thyristors responding to the rate of voltage change can be turned on 

by a surge13, resulting in failure of the device or hazardous energizing of the load they control. In a 

similar way, a triac may be turned on by a voltage surge without damage, but still fail by exceeding the 

peak power limit during a surge-induced turn-on with slow transition time. 

4. Power conversion equipment, with a front-end dc link where the filter-capacitor voltage can be 

boosted by a surge, resulting in premature or unnecessary tripping of the downstream inverter by its 

own on-board overvoltage or overcurrent protection schemes. 

5. Data-processing equipment, where malfunction (data errors) -- not damage -- may be caused by fast 

rate of voltage changes (capacitive coupling) or fast rate of current changes (inductive coupling) that 

reflect the initial characteristic of the surge event. This response is insensitive to the "tail" of the surge, 

where all the "energy" would be contained according to the misleading energy-related concept. 

6. Light bulbs, which of course have a limited life associated with filament evaporation and 

embrittlement -- a long-term process where the short burst of additional heating caused by a few 

microseconds of overcurrent is negligible -- but also fail under surge conditions when a flashover occurs 

within the bulb, triggering a power-frequency arc that melts out the filament at its point of attachment -- 

another failure mechanism originating with insulation breakdown. 

Among these types of victims, only the clamping-type varistor is directly sensitive to an energy level 

associated with a surge event -- and at that, the energy deposited in the device, not the "energy in the 

surge." Considering the explosive proliferation of varistors, however, one might find some extenuating 

circumstances in emphasizing the significance of energy in describing the effect of surges on its 

principal target -- the ubiquitous metal-oxide varistor -- but this is a pitfall, a mental trap. 
Table 1 

Significant Surge Parameters (X) in Equipment Failure Modes 

Surge parameters 

Type of equipment Source Peak Maximum Tail Repetition 12t in 

impedance voltage rate of duration rate device* 

amplitude voltage rise 

Insulation - Bulk X X ** - Windings X X 

- Edges X X 

Clamping SPDs - Bulk X X X X X 

- Boundary X X 

Crowbar SPDs X X X X X 

Semiconductors - Thyristors X X X 

- Triacs X X X X 

- IGBTs X X X 

Power conversion - DC level X X X X 

- Other X X 

Data processing malfunction X X X 

* The Pt in the device is actually the result of the combination of surge parameters and device response to the surge. 

Like other power and energy-related equipment stress, 3t is not an independent parameter of the surge. * * Amount of final carbonization, not the initial breakdown. 

Baiting The Trap 

From the interactions described above, it is clear that using a single voltage measurement to determine 

surge threat is not sufficient. The trap was baited by the simplicity and ease of using a single parameter 

obtained by analogy with the power dissipated in a fixed resistance, d/R by an instantaneous voltage, v. 

Clearly in that limited case, the total energy involved over the surge event would be the time integral of 

$/R, expressed by a number having the same dimensions as watt-seconds, or joules in the SI system. 

And thus some power quality monitors placed on the market in the early eighties were printing out 

surge event characterizations expressed in joules. This "joule" number was obtained by computation of 

the jiv2/~.dt, where the voltage v was measured by the instrument, divided by a resistance (taken 

arbitrarily as 50 a), and integrated over the duration of the event. Manufacturers of power quality 

monitors soon recognized the potentially misleading aspects of such reporting and discontinued the 

practice. 

Nevertheless, some researchers continued the practice and are to this day attempting to characterize the 

surge environment by the single parameter of "energy in the surge." As a half-way measure, some are 

now proposing a new parameter "specific energy" to be understood as the integral of voltage-squared 

divided by a reference resistance of 50 SI (why that particular value ?) and they would report results in 

watt-seconds. Figure 1 shows an example of this type of reporting14. 

We completely agree that, indeed, the selection of an appropriate varistor should reflect the level of 

threat to which it will be exposed, so that there is a need to characterize the threat in terms of the energy 

that will be deposited in the varistor by a specific surge event. However, there is no way that a 

voltmeter measurement only, even if it includes time, can provide that information. This observation 

was presented at an earlier Power Quality Conference1', and discussions in that forum, as well as in 

working groups developing standards on the surge environment, indicated the need to give a wider 

distribution to the message, hence this paper in this forum. 
W [mws] 

Figure 1 - Example of report of survey results l4 with number 

of occurrences as a function of "energy" in milliwatts-seconds 

Thesis Demonstration by Varistor Applications 

To demonstrate our thesis by the ad absurdurn process, we will compute the "energy in the surge" as 

defined by the trap-baiting definition of "specific energy" for three surge events such that all have the 

same "specific energy" but different voltage levels, waveforms, and durations. Then, making a further 

assumption for the unknown impedance of the surge source, we will compute the energy actually 

dissipated in the varistor for these different voltage levels, waveforms, and durations, and observe that 

the resulting deposited energy is not the same ! 

Elementary example: basic calculation with fixed impedance 

As a first easy-to-follow step, we take three rectangular pulses, all selected to have the same "specific 

energy" but different voltage levels and corresponding durations, and compute the energy deposited in a 

nonlinear varistor having a given maximum limiting voltage, assuming that the source of the surge is a 

voltage source with some arbitrary, fixed impedance. It is noteworthy that some source impedance has 

to bepresumed, because the varistor clamping action rests on the voltage divider effect of the source 

impedance and the dynamic (variable) varistor impedance prevailing for the resulting current. 

Start with an assumed surge measurement of 1000 V with duration of 50 ps. The "specific energy" of 

such a surge event, according to the proposed definition, is: 

(1000 v)~ x 50 ps / 50 Q = 1 joule. 

Now consider a surge with a peak amplitude of 3 16 V (3 16 = 1000 / 410) and a duration of 500 ps 

(500 = 50 x 10). Its "specific energy" is: 

(3 16 v)~ x 500 ps / 50 Q = 1 joule. 

To complete the bracketing range, consider a surge of 3 160 V (3 160 = 1000 x dl 0), and a duration of 

5 ps (5 = 50110). Its "specific energy" is: 

(3160 v)~ x 5 ps / 50 Q = 1 joule. 

We now apply each of the three voltage surges to a 130-V rated varistor (200 V at 1 mA dc), 

assuming an arbitrary source impedance of Z, = 1 Q. One can compute the resulting current or, for this 

simple example, make a fast-converging manual iteration without the help of a computer, as follows: 
(a) assume a current I, and look up the resulting voltage V, on the varistor I-V characteristic; 

(b) compute [Z, x 4; 

(c)is[ZLyxI]+ VV=lOOOV? 

(d) If yes, I is correct, the energy deposited in the varistor is 

Ix VVxAt 

If no, go back to (a) with a converging assumption for I. 

Table 2 shows the results from this manual iteration for the three surges defined above. It is quite 

apparent that the constant "specific energy" for the three surges does not result in the same energy 

deposition. The dynamic impedance (VJI) of the varistor is also shown, to illustrate the well-known 

theorem that the power dissipated in a resistive load reaches a maximum for matched source-load 

impedance. This theorem is yet another reason why a surge to be applied to a varistor cannot be 

characterized in the abstract: one needs to know the source impedance (real and imaginary components) 

as well, to assess the energy sharing between source and load. 

Table 2 

Energy Deposited in a Varistor by a Surge, as a Function of Surge Parameters, 

All Surges Having a 1 Joule "Specific Energy" for a Source Impedance of 1 Ohm 

Rectangular Surge 

Parameters 

Source/Varistor Response to Surge 

Postulated Postulated "Specific Varistor Varistor Varistor Power in Energy in 

amplitude duration energy" current voltage impedance varistor varistor 

(V> (PSI (J) (A) (V) (Q) (W) (J) 

Computer calculation with multiple combinations 

We now compute the energy deposited in three varistors of three different maximum limiting voltages, 

for two combinations of voltage levels and durations that produce the same "specific energy," each with 

classical waveform (Ring Wave or Combination Wave), sized to produce 1 joule of energy dissipation 

in a 50-8 resistor, according to the classical formula cited earlier, and for three values of source 

impedance. We can anticipate that the peaks will be quite different, foreboding very different effects on 

equipment. In fact, the peaks turned out to be 3 kV and 1.2 kV, respectively for the two waveforms. 

Applying these two waveforms to a family of varistors typically used in 120-V or 240-V power systems, 

we computed the energy deposited in these varistors for three arbitrary source impedances (assumed to 

be ohmic), using the EMTP programI6 to input closed-form equations for the open-circuit surge voltage. 

The results are shown in Table 3. These simple illustrations show that even the concept of "specific 

energy" proposed as an improvement over the concept of "energy in the surge" cannot be used to select 

a candidate varistor energy-handling rating, and serves no useful purpose in characterizing the surge 

environment. 
Table 3 

Energy Deposited in Varistors by Ring Wave and Combination Wave "1 Joule Surges" 

For Different Source Amplitudes and Varistor Nominal Voltages 

Surge parameters Source Varistor nominal Peak current Energy deposited -7 A 

(All for 1 J) impedance (Q) voltage (V) in varistor (A) in varistor (J) 

130 2732 7.97 

1 150 2677 8.53 

Ring Wave 275 2245 10.7 

100 kHz 130 239 0.55 

0.5 ps rise time 12 150 234 0.60 

(3 kV peak) 275 208 0.8 1 

1 150 73 9 10.7 

Combination 275 426 6.24 

Wave 130 72.1 0.87 

1.2/50 ps 12 150 68.4 0.89 

(1.2 kV peak) 275 45.0 0.64 

130 17.7 0.21 

50 150 17.1 0.21 

275 11.4 0.16 

Conducting Future Surveys: Make Recordings That Make Sense! 

Recording Relevant Parameters 

In an effort to acknowledge the legitimate quest for the single number characterization, we should offer 

alternatives, not just stay with a negative vote The solution might be to tailor the surge characterization 

to the intended application, that is, take into consideration the failure mode of the specific equipment, 

and present the data in a form most suited for that equipment. Of course, this would mean not only 

avoiding a single number, but actually providing combinations of parameters, each combination best 

suited to a particular type of victim equipment, according to their failure modes. 

The recently-approved IEEE Recommended Practice Std 11 59 on Monitoring Power Quality17 offers 

some guidance on conducting surveys, including not only surges, but other parameters. The Working 

Group that developed this standard has now established task forces to develop further recommendations 

on processing and interpreting the recorded data, including more uniform formats. 

Table 1, discussed earlier, presented a matrix of surge parameters and types of equipment, showing for 

each type of victim which surge parameter is significant or insignificant. In compiling that table, the 

authors sought to identify all types of potential victims. As it turned out, the term [I? x dt] or its 

integral, alone, is not directly involved in the failure of any of the equipment listed in Table 1. A more 

complete set of data, associated with specific equipment sensitivity, will be needed to characterize the 

surge environment and achieve compatibility between that environment and equipment to be installed. 
The fallacy of present-day voltage measurements 

Another consideration that must be observed in conducting and reporting the monitoring of surges is the 

proliferation of SPDs in end-user installations. It is unlikely today to find an installation where some 

SPD is not present, either as a deliberate addition to the system, or as part of the connected equipment. 

Aware of this situation, some researchers have attempted to disconnect all known SPDs from the system 

being monitored so that results would represent the "unprotected location" situation such as that initially 

described in IEEE 587-1980'~, the forerunner of ANSIAEEE C62.41-199119. 

However, even this precaution of disconnecting all known SPDs does not guarantee that some 

undetected SPD might not have been left connected somewhere and thus invalidate the record. Thus, 

extreme caution must be applied to reporting and interpreting voltage monitoring campaigns conducted 

after 1980 20. 

We now propose a change in the protocol for the monitoring of power quality in ac power systems. 

This change has become necessary because end-user power systems are no longer what they were at the 

time the early surveys of transient overvoltages were conducted, a time at which measuring transient 

voltages did indeed make sense. Varistor-based surge-protective devices (SPDs) have become so 

ubiquitous in low-voltage ac power systems that hardly any location can be found where there is not 

some form of transient voltage limitation in effect. Attempting now to characterize the environment so 

that appropriate SPDs could then be prescribed for specific locations based on voltage measurements 

would be quite misleading. What such a measurement would yield today is no longer the surge 

characteristics of the monitored system, as it was at the time of the early surveys, but the residual 

voltages of whatever SPDs are installed nearby. 

Making meaningful measurements 

The proposed change in monitoring practices is to insert a current transducer between the low-voltage 

power system being monitored and the existing monitoring instruments. This transducer would consist 

of an SPD with the minimum tolerable voltage rating across the power line, to be connected at some 

point of an installation, and serve as a "magnet" for attracting the impinging surges. To use a metaphor, 

this SPD in effect becomes the "winning bidder" by offering to the impinging surge the path with lowest 

clamping voltage among all the parallel-connected SPDs of the installation. 

A current transformer with the "magnet SPD" in the primary and an appropriate burden on the 

secondary (Figure 2) would be used to feed the resulting voltage signal into the existing power quality 

monitoring instruments now used by many organizations and individual researchers. Typically, the 

voltage channels have higher frequency rsponse that current channels. In this manner, the surge current 

attracted by the "magnet SPD" can be recorded to find the true character of surge events at that 

particular location, despite the presence in the local system of any and many unknown and uncontrolled 

SPDs. 

- - 

Figure 2 - Schematic of the transducer 

8 
The current transducer would consist of a string of silicon avalanche diodes (SADs) in series with the 

primary of a current transformer with a burden connected across its secondary, an overcurrent protective 

fuse in series with the diodes, and an indicating light to signal a blown fuse. Because the very principle 

requires that the SAD string have a clamping voltage lower than any other SPD in the installation, it 

would be the most vulnerable to a large swell. To remove the transducer from the system in case of 

failure of the SAD string, the fuse is provided ahead of the transducer circuits. 

In the final design that would be used to deploy a number of these transducers, all of these components 

would be included in a package derived from the so-called "plug-in SPD" which are offered by many 

manufacturers. Using the external package of such a device will provide a low-cost envelope to build a 

few hundred transducers with no tooling costs and yet provide a package suitable for connection to wall 

receptacles in end-user systems. 

It should be noted that only one channel of the monitor need to be allocated for recording the surge 

current. While the determination of power and energy deposited in the SAD requires knowledge of 

three parameters: current, voltage, and time, for the calibrated SAD built in the transducer, the voltage 

can readily be computed from the device I-V characteristic when the current waveform is known. 

Preliminary results on the feasibility of such a recording system have been obtained: a suitable silicon 

avalanche diode has been identified and proven to act as a "magnet," even in the presence of 

"competing" metal-oxide varistors, and yet able to withstand the temporary overvoltages that can occur 

in the system. The current transformer can be any of readily available low-cost transformers; for the 

purposes of recording the surge events in the environment, the exacting accuracy of a laboratory-grade 

pulse current transformer would not be necessary. 

The power system can include several branch circuits to supply the loads, some of which featuring 

SPDs incorporated into load equipment or installed by the end-user. At some point of this system, 

selected for convenience by the instrument operator, the transducer will be installed. A key point of the 

proposal is that pinning down the actual location of the monitor is no longer a concern because of the 

"magnet" effect of the low-clamping SAD string. 

By design, the string of diodes is intended to become the "magnet" that will attract the impinging 

surges. We recognize that this winning bid can be ensured only within a certain radius from the 

transducer. Increasing distances between the transducer and competing SPDs eventually produces a 

decoupling of the two devices and might allow a competing SPD connected upstream from the 

transducer to divert the surge first. This situation is the reverse of that sought when making studies of 

the coordination of cascaded SPDs, where the concern is to ensure that a heavy-duty SPD located 

upstream of a lower-duty SPD is sufficiently decoupled so that an impinging surge will be diverted by 

the upstream SPD. The parameters of cascade coordination have been addressed at length in the 

literature *' 22 23 24 and will not be discussed here. For typical circuit lengths in a low-voltage 

installation, our tests have demonstrated that the SAD string of Figure 2 offers a sufficiently low voltage 

path for impinging surges that it will indeed be the magnet. 

More sophisticated analysis can be performed by applying the numerical modeling techniques 

developed in the referenced modeling studies extending the distances and combinations of 

competing SPDs to determine how extensive an installation can be and still have the transducer remain 

the winning bidder. In this manner, the pitfall that threatens credibility of contemporary voltage 

recordings (uncertainty about other unknown SPDs connected in the system that can produce 

misleading results of low surge activity) will be eliminated. 
Program Implementation 

The next step in making the change from surge voltage recording to surge current recording would be to 

recruit enough participants willing to acquire the transducer and use their existing commercial 

monitor(s) to record the occurrences of surge currents attracted by the transducer. The transducer could 

be produced in cooperation with a manufacturer of a plug-in SPD, so that a readily adaptable outside 

package could contain the transducer components and provide a simple and safe way of connecting it to 

a receptacle. 

Within the IEEE, a new Task Force of the Standards Coordinating Committee on Power Quality SCC22 

is developing protocols for reporting monitoring results; hopefully, the concepts presented in this paper 

will be taken into consideration by that Task Force and by other organizations interested in making 

surveys for characterizing the electromagnetic environment. The IEC is also developing guidance 

documents on measurement methods in the area of power quality, where this shift of focus should be 

taken into consideration. 

Conclusions 

The attempt to characterize the surge environment by a single number -- the "energy in the surge" or 

"specific energy" -- is a misleading approach that should most definitely not be used in Power Quality 

research. There are at least four reasons for this prohibition: 

1. The concept that energy can be defined in the abstract from a single measurement of voltage across 

the lines of an undefined power system is a faulty oversimplification. 

2. The potential victims of a surge event have responses that reflect their design and for many, their 

failure modes can be totally independent of any energy consideration. 

3. The prime interest of energy consideration is related to the energy-handling capability of metaloxide varistors. The energy deposited in such a device by a given surge event depends on 

amplitude, waveform, source impedance, and varistor characteristics, and not on the "effective 

energy." 

4. Last but not least, the proliferation of surge-protective devices (SPDs) in low-voltage, end-user 

facilities makes the recording of surge voltages a fallacy as the recorded voltages now represent the 

response of the installed (and generally unknown) SPDs in the installation, not the actual threat of 

impinging surges. That threat can now only be assessed by installing an instrument that will attract 

impinging surges to itself and measure the current that can be delivered by the surge. 

Future surveys should be conducted keeping in mind the relevant parameters for characterization such 

as peak amplitude, maximum rate of rise, tail duration -- but not "energy." Relevant and realistic 

assessment of surge stress threats must consider not only all the characteristics of a surge event, but also 

the source of the surge and the failure mechanisms of potential victim equipment. Standards-writing 

bodies concerned with characterizing the electromagnetic environment in low-voltage power systems 

could make an important contribution by giving recognition to the new situation and shifting focus from 

surge voltage measurements to surge current measurements. 

Acknowledgments 

support lor tne aevelopment or tnls paper was prOVlded by the authors' parent organizations and by the 

Power Quality research group of Pacific Gas & Electric. Gerald FitzPatrick and Thomas Key provided 

comments on the initial two papers l5>*O from which this new paper has been developed. 
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15. Key, Mansoor, and Martzloff, "No Joules for Surges: Relevant and Realistic Assessment of Surge 

Stress Threats," Proceedings, IEEE International Conference on Harmonics and Power Quality, 

Las Vegas, October 1996. 

16. EPRI Report EL-642 1 -L, Electromagnetic Transient Program (EMTP), Version 2.0, Volumes 1 

and 2, July 1989. 

17. IEEE 1 159- 1995, IEEE Recommended Practice for Monitoring Electrical Power Quality. 

18. IEEE 587-1980, IEEE Guide on Surge Voltages in Low-Voltage AC Power Circuits. 
19. ANSIAEEE C62.41- 199 1, Recommended Practice on Surge Voltages in Low- Voltage AC Power 

Circuits. 

20. Martzloff, "Surge Recordings that Make Sense: Shifting Focus from Voltage to Current 

Measurements," Proceedings, EMC '96 ROW Symposium, Rome, Italy, September 1996. 

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Transactions, IAS-29 No.4, JulyIAugust 1993, pp 680-687. 

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systems: Needs for secondary protection," In Proceedings, 20th International Conference on 

Lightning Protection, 1992. 

23. Rousseau and Perche, "Coordination of Surge Arresters in the Low-Voltage Field," In Proceedings, 

17th International Telecommunications Conference (INTELEC 95), 95CH35824, pp 11 9-125. 

24. Martzloff, Mansoor, Phipps, and Grady, "Surging the Upside-Down House: Measurements and 

Modeling Results," In Proceedings, PQA '95 Conference, EPRI, 1995.