2000-030-0153-1

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Measurement guide for voltagecharacteristics

......................................................................................................

Electricity product characteristics andelectromagnetic compatibility......................................................................................................

July 1995Ref : 23002Ren9531

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1 International Union of Producers and Distributors of Electrical Energy2 European Grouping of Electricity Undertakings

Measurement guide for voltage characteristics

............................................................................................

Electricity product characteristics andelectromagnetic compatibility............................................................................................

Paper prepared by:

Roger OTT (FR); Gerrit BLOM (NL); Michel DUSSART (BE); PierreFERRAND (FR); Peter LODERER (AT)

The work has been started by Andr MENDES (FR) and was carried outwith the contribution of Jean-Louis JAVERZAC (FR), Richard NOTTELET(FR) and Pierre PICARD (FR)

Copyright Union of the Electricity Industry - EURELECTRIC, 2000

All rights reservedPrinted at EURELECTRIC, Brussels (Belgium)

CONTENTS

Part 1: General ................................................................................................................ 2

1.1 Introduction ..................................................................................................... 2

1.2 Normative references........................................................................................ 3

1.3 General and environment .................................................................................. 4

1.4 Auxiliary supply voltage ................................................................................... 11

1.5 Measurement transformers ............................................................................... 12

Part 2: Specification of measurement methods .............................................................. 13

2.1 Power frequency .............................................................................................. 14

2.2 Magnitude of the supply voltage....................................................................... 15

2.3 Rapid voltage changes: flicker severity ............................................................. 16

2.4 Supply voltage dips .......................................................................................... 17

2.5 Short and long interruptions ............................................................................. 19

2.6 Temporary power frequency overvoltages between live conductors andearth................................................................................................................ 20

2.7 Transient overvoltages between live conductors and earth ................................ 22

2.8 Supply voltage unbalance ................................................................................. 22

2.9 Harmonic voltage ............................................................................................. 23

2.10 Interharmonic voltage..................................................................................... 25

2.11 Mains signalling voltage ................................................................................. 25

Part 3: Withstand and immunity characteristics........................................................... 26

3.1 Permanent monitoring ...................................................................................... 26

3.2 Temporary surveying or general purpose investigations: general mechanicalrequirements.................................................................................................... 28

23002Ren9531 July 19951

SUMMARY

The purpose of this report is to provide a practical approach for measuring andevaluating the characteristics of supply voltage as specified by the European standard EN50160, issue of November 1994.

The problem has been analysed with a view of the different situations which canoccur in practice:

- permanent verification of supply characteristics, depending on contractualobligations

- temporary surveying motivated by distributor's requirements or by user's complaints

- surveys to check the performance of a supply system for general purposeinvestigations.

After having defined the reference environmental conditions and the requiredoperating characteristics of the measuring instruments, the report describes the measurementmethods and the information processing criteria for the evaluation of each of the voltagecharacteristics considered in the European standard.

This document provides a suitable solution for the assessment of the voltagecharacteristics and represents an effective contribution of UNIPEDE to the definition of acomplete frame of reference for the electricity supply service, according to the general policybeing pursued by the European Union.

23002Ren9531 July 19952

PART 1: GENERAL

1.1 Introduction

The CENELEC standard EN 50 160 defines the voltage characteristics of theelectricity supplied by medium voltage and low voltage public distribution systems at the userssupply terminals.

To check the compliance of the actual voltage characteristics with the EN standard itis necessary to provide more detailed information on measuring and evaluation methods.

Moreover the functional and constructive specifications for the measuring equipmentshould be established with reference to the application requirements and the relevantinternational standards.

The aim of this report is to describe a possible approach to the measurement andcompliance verification of the voltage characteristics for which the EN gives definite values,by giving the measurement techniques and the performance characteristics with which theinstruments intended to be used should comply with.

The document is subdivided into three parts:

- Part 1 General,

- Part 2 Specification of measurement methods,

- Part 3 Withstand and immunity characteristics.

Three categories of application have been considered:

- 1st category: permanent monitoring (for example for contractualverifications),

- 2nd category temporary surveying (for example to check the performance ofthe supply system, or in case of user complaints),

- 3rd category for general purpose investigations.

For each of these categories specific requirements exist, in particular those dealingwith environmental conditions.

As far as these requirements are concerned, the report deals only with the influencingfactors which should be complied with for each category.

When some parameters are not expressly given, it is understood that they are left tobe declared by the manufacturer.

The guidelines given in the report may also be used for verification of voltagecharacteristics with tolerances different from those stated in the EN 50160 Standard, bymaking the necessary modifications.

23002Ren9531 July 19953

1.2 Normative references

IEC CENELEC TITLE

EN 50160

Voltage characteristics of electricity supply bydistribution systems

IEC 60 High-voltage test techniques

IEC 68 Environmental testing

IEC 85 Thermal and evaluation and classification of electricalinsulation

IEC 186 & 186A Voltage transformers

IEC 255 Electrical relays

IEC 529 Degree of protection provided by enclosures (IP code)

IEC 695 Fire hazard testing

IEC 868 EN 60868 Flickermeter - Functional and design specifications

IEC 801-2 Electrostatic discharge requirements

IEC 801-3 Radiated electromagnetic field requirements

IEC 801-4 Electrical fast transient/burst requirements

IEC 817 Spring-operated impact-test apparatus and itscalibration

IEC 1036 EN 61036 Alternating current static watt-hour meter for activeenergy (classes 1 & 2)

IEC 1000-2-2 Electromagnetic compatibility

IEC 1000-4-5 Surge immunity tests

IEC 1000-4-7

General guide line on harmonics and inter harmonicsmeasurements and instrumentation, for power supplysystems and equipment connected thereto

IEV 50(301) General terms on measurements in electricity

CISPR 22 EN 55022 Limits and methods of measurement of radiointerference characteristics of Information technologyequipment

23002Ren9531 July 19954

1.3 General and environment

1.3.1 Organisation of the measurements

The voltage to be measured is either directly accessible as it is generally the case inlow-voltage supply systems, or accessible via measurement transformers. The instrumentationperforms the measurement of certain voltage characteristics by means of an analog, digital orother data acquisition technique. As a last step, the measured parameters are subjected to aconditioning which is most often meant to eliminate the effect of spurious phenomena andprocessed for evaluation.

This principle is illustrated by the following figure.

Measurement transformers

Measurement unit

Evaluation unit

Um : voltage to be

measured

Us : voltage

supplied

Gm : measurement

result

Ge : measurement evaluation

Figure 1: Block diagram of a measurement chain

The term measurement instrumentation theoretically covers the whole chain betweenthe voltage supplied and the measurement evaluation. For the purpose of this guide the term"measurement instrumentation" will be restricted to the blocks "measurement unit andevaluation unit". In particular, the requirements dealing with accuracy will only apply to theseunits, the specifications for measurement transformers being defined separately.

1.3.2 Environment

1.3.2.1 General

The voltage characteristics given in the standard EN 50 160 are related to normaloperating conditions, so that when making evaluations it is to be intended that any timeinterval in wich the supply system is not in normal operating conditions (e.g. interruptions,faults, etc.) should be excluded from the evaluation.

The measurement of a specific voltage characteristic can be affected by the variationof another characteristic of the voltage measured. As a consequence, influence quantities

23002Ren9531 July 19955

include the characteristics of the measured voltage given by CENELEC standard EN 50 160 inaddition to "external" influence quantities.

Moreover, the supply of the measurement system shall be designed in such a way thatit has no significant effect on the measurement result when the auxiliary supply voltage is itselfdisturbed.

Several variation fields for parameters are defined for each category. These are:

- reference conditions,

- specified operating range,

- limit range of operation,

- storage and transportation conditions.

The influence quantities wich are not mentioned in the following tables shall bespecified by the equipment manufacturer of the measurement.

The connection devices of "voltage" circuits must comply with safety rules and withrelated regulations.

1.3.2.2 Reference conditions

Definition of influence quantity Any quantity, generally external to the measurementequipment, which may affect its working performance (IEV 301-08-09 modified).

Definition of reference conditions Appropriate set of influence quantities and performancecharacteristics, with reference values, their tolerancesand reference ranges, with respect to which the intrinsicerror (e r ) is specified (IEV 301-08-10 modified).

The basic reference conditions (influence quantities with their reference values andtolerance) are reported in the following table:

23002Ren9531 July 19956

Influence quantity Nominal Permissible tolerance

Frequency 50 Hz 0.5 Hz

Voltage magnitude nominal value 1 %

Flicker (Pst) 0 0.1

Voltage dips 0 0

Interruptions 0 0

Transient overvoltages 0 IEC 1000-4-5, level 1

Unbalance 0 0.5 %

Harmonics (THD) 0 3 %

Interharmonics (at any frequency) 0 1 %

Ripple control signals 0 1 %

Ambient temperature 23C 2C

Humidity 50 % 10%

Magnetic induction of external origin atthe reference frequency (50 Hz)in any

direction

0 0.05 mT(1)

External electric field at referencefrequency (50 Hz) in any direction

0 0.1 kV/m

Auxiliary supply voltage see sub-clause 1.4

Air absence of corrosive atmosphere

These reference conditions are valid for categories 1, 2 and 3 equipment.

(1) IEC 1036 table 19 page 67.

23002Ren9531 July 19957

1.3.2.3 Specified operating range

Definition of specified operating range Range of values of a single influence quantitywhich forms a part of rated operatingconditions (3.6.9 IEC 1036).

1.3.2.3.1 Operating range for category 1

Influence quantities Range Accuracy

Frequency 42,5 Hz - 57,5 Hz

Voltage magnitude nominal 15 %

Flicker (Pst) 0 - 4

Voltage dips up to 1,5 s ; 99%

Interruptions up to 4 hours(2)

Unbalance 0 - 5(3) %

Harmonics (THD) 0 - 15 %

Interharmonics (at any frequency) 3 % e r Ripple control signals 0 - 9 %

Ambient temperature -10C - + 45C

Humidity 20% - 95 %

Magnetic induction of external origin atthe reference frequency (50 Hz) in any

direction

up to 0,5 mT(4)

External electric field at referencefrequency (50 Hz) in any direction

up to 1 kV/m

Transient overvoltages 6 kV (IEC 1000-4-5)

Electrostatic discharges 15 kV (IEC 801-2)

Electromagnetic HF fields 10 V/m (IEC 801-3) 2 e r Fast transients 2 kV (IEC 801-4) 2 e r



(2) Only valid for time measurement accuracy.(3) Only valid for polyphases measurements - see part 2.(4) IEC1036 table 14 page 45.

23002Ren9531 July 19958

The accuracy e r is specified for each measurement mode (refer to Part 2).

In addition to this, for a permanent installation the measurement device shall haveimmunity to mechanical and external electromagnetic stresses. These are described in Part 3.

1.3.2.3.2 Operating range for category 2.


Frequency 42,5 Hz - 57,5 Hz

Voltage magnitude nominal 15 %

Flicker (Pst) 0 - 4

Voltage dips up to 1,5 s ; 99%

Interruptions up to 4 hours(5) 2 e r Unbalance 0 - 5 %


Interharmonics (anyfrequency)

3 %

Ripple control signals 0 - 9 %




(5) Only valid for time measurement accuracy.

23002Ren9531 July 19959

3.2.3.3 Operating range for category 3


Frequency 42,5 Hz - 57,5 Hz 2 e r Voltage magnitude nominal 15% 2 e r

flicker (Pst) 0 - 4

Unbalance 0 - 5 %

Harmonics (THD) 0 - 15 % 4 e r Interharmonics (at every

frequency)3 %

Ripple control signals 0 - 9 %

Transient overvoltage 0,5 kV (IEC 1000-4-5)

Ambient temperature +15C, + 30C 2e r Auxiliary supply voltage see sub-clause 1.4


1.3.2.4 Limit range of operation

Definition of limit range of operation Extreme conditions which an operatingmeasurement equipment can withstand withoutdamage and without degradation of itsmetrological characteristics when it issubsequently operated under its rated operatingcondition (3.6.10 IEC 1036).

23002Ren9531 July 199510

1.3.2.4.1 Limits for category 1

Influence quantities Range

Voltage magnitude 0 to 1.25 U nominal

Ambient temperature -20C, + 55C

Humidity 10% - 100 %



Air absence of corrosiveatmosphere

Electromagnetic influence quantities are given in Part 3.

1.3.2.4.2 Limits for categories 2




1.3.2.4.3 limits for categories 3



Transient overvoltages 0.5 kV (IEC 1000-4-5)

1.3.2.5 Storage and transportation conditions

Definition of storage and transportationconditions

Extreme conditions which a non-operatingmeasurement equipment can withstand withoutdamage and without degradation of itsmetrological characteristics when it issubsequently operated under its rated operatingcondition (3.6.11 IEC 1036).

23002Ren9531 July 199511

1.3.2.5.1 Conditions for category 1


Ambient temperature -25C, + 70C

Humidity 10% - 100 %


1.3.2.5.2 Conditions for categories 2 and 3

No mandatory additional requirement.

1.4 Auxiliary supply voltage

The table below gives the requirements of auxiliary supply voltage for auxiliarysupply interruptions.

The magnitude and two different durations of the interruption of the auxiliary supplyvoltage interruption are considered:

- t1: duration during which the measurement equipment continues its normaloperating mode.

- t2: duration during which the measurement equipment keeps the time.

Categories Permanent operation Back-up operation

1 Un 25%

From 0 to 75% Un

t1= 4 minutes

t2= 4 hours

2 Un 15%

From 0 to 85% Un

t1: not specified

t2= 4 hours

3 Un 15%

From 0 to 85% Un

t1: not specified

t2: not specified

23002Ren9531 July 199512

1.5 Measurement transformers

1.5.1 Connection arrangement

The instrumentation is connected between phases or between phase and neutraldepending on the measurement requirements.

If the instrumentation is installed behind measurement transformers, the connection ofvoltages directly applied to the instrumentation shall be the image of the voltages delivered bythe distributor (phase-phase or phase-neutral voltages).

If, for cost reasons for instance, the measurement is made at the supply transformersecondary terminal, the voltage characteristics are not exactly the same as at the transformerprimary. The interpretation of the measurement results is delicate and is not dealt with in thepresent guide. It may nevertheless be agreed upon between distributor and customer.

1.5.2 Main characteristics of measurement transformers

The single-phase voltage transformers required for the measurement of thecharacteristics of the "Medium Voltage" comply with IEC recommendations 186 and 186 A.These transformers are wound-type transformers with a magnetic core.

The voltage at the secondary terminal of a measurement transformer is standardisedand is either equal to 100 V/3 , 110 V/3, 100 or 110 V (at present 200 V).

The rated burden of measurement transformers is limited. It shall not exceed 25 VAin all cases. The accuracy class is 0.5.

The accuracy of voltage transformers, in frequency range from 45 Hz to 2000 Hz isbetter than 5 %.

1.5.3 Influence of existing voltage transformers

As far as these devices are concerned, before any measurement, it will be necessary tocheck the compliance of their characteristics with the recommendations of IEC 186 and 186 Aand sub-clause 1.5.2.

Single-phase capacitor (VCT) transformers complying with IEC recommendationsmay be used for the measurement of the voltage characteristics, except for the measurement ofharmonic and interharmonic voltage.

23002Ren9531 July 199513

PART 2: SPECIFICATION OF MEASUREMENT METHODS

Each measurement mode for instrumentation is specified as follows:

- requirements on measurement accuracy

- requirements for influence quantities on the disturbances of the voltage to bemeasured.

For each measurement mode the accuracy is specified, unless otherwise indicated,assuming that the other influencing magnitudes on the voltage to be measured are under theirreference conditions as defined in Part 1, sub clause 1.3.2.2.

Notes

1) - Except for frequency measurements, the instrumentation concerns either singlephase or phase to phase connections

2) - Unbalance measurement is specific to polyphase systems.

In the following, for each measurement mode, the measurement evaluation is carriedout on the basis of the the valid samples.

A sample is considered valid if the mean value of the voltage over the applicablespecified basic fixed time interval, measured as stated at sub-clause 2.2.1, remains within therange 15 % of the supply nominal (or declared) voltage.

The basic fixed time intervals used in the different measurement modes are thefollowing:

- for power frequency: 10 seconds

- for magnitude of the supply voltage, flicker severity, and supply voltage unbalance:10 minutes

- for harmonic/interharmonic voltages: 3 seconds and/or 10 minutes

- for mains signalling voltages: 3 seconds.

As an example, for the measurement of the supply voltage magnitude, the followingapproach is applied:

- Number of 10-minute intervals in the observation period of one week: 1008

- Number of non valid 10-minute intervals (intervals with mean voltage outside the15 % tolerance): Nnonvalid

- Number of valid 10-minute intervals (intervals with mean voltage within the 15 %tolerance): 1008-Nnonvalid = N

23002Ren9531 July 199514

- Number of valid 10-minute intervals with voltage not complying with EN 50160(intervals with voltage outside the tolerance of 10 % and within the tolerance 15%): N1,

Compliance with EN 50160 is given by: 1N1008 nonvalidN

1NN

5%-

=

2.1 Power frequency

2.1.1 Measurement

Frequency measurement is a mean value over 10 seconds fixid time intervals.

2.1.2 Specification of the instrumentation

When an a.c. voltage that fulfills requirements of reference conditions is applied at theinstrumentation input, the instrumentation presents an intrinsic error e r :

e r 50 mHz

for categories 1,2 and 3.

2.1.3 Influence quantities at the specified operating range

For this measurement mode, the range of one of the influence quantities given in sub-clause 1.3.2.3 Part 1 is extended. The following table gives the variation range of theconcerned quantity:

Nature Variation range

Harmonics (THD) 0-20 %

Note:

Accuracy is given in Part 1: table of sub-clause 1.3.2.3.1 for category 1 equipments, table ofsub-clause 1.3.2.3.2 for category 2 and table of sub-clause 1.3.2.3.3 for category 3

2.1.4 Measurement evaluation

- Observation period of one week in fixed steps of 10 seconds

- Determination of the number of 10 s intervals during which:

- the supply voltage is within 15 % of its nominal value(6) : N

- the frequency differs by more than 0.5 Hz from the nominal value and the supplyvoltage is within 15 % of its nominal value: N1

(6) Mean arithmetic value over a then minutes time period.

23002Ren9531 July 199515

- the frequency differs by more than - 3 Hz, + 2 Hz from the nominal value and thesupply voltage is within 15 % of its nominal value: N2

2.1.5 Nominal value and limits for compliance

Nominal value:

f n = 50 Hz

The requirements of the standard are fulfilled if:

N1/N 5%

and N2=0

2.2 Magnitude of the supply voltage

2.2.1 Measurement

The instrumentation shall measure the r.m.s. voltage(7) . Each basic measurementvalue is the mean value over a fixed 10 minutes time period. Every measurement updatesprevious one at the end of the 10 minutes period.


When an a.c. voltage that fulfills requirements of reference conditions is applied at theinstrumentation input, the instrumentation presents with respect to the nominal value anintrinsic error e r less than:

- for category 1 equipment: 0.5 %,

- for category 2 equipment: 0.5 %,

- for category 3 equipment: 1 %.

(7) The r.m.s. value U of a signal u(t) is defined by the relation *=T

tdtuT

U0

2 )()(1

. T is equal to a

period time (according to IEC definition).

23002Ren9531 July 199516




Harmonics (THD) 0-20 %

Note: Accuracy is given in Part 1: table of sub-clause 1.3.2.3.1 for category 1 equipments,table of sub-clause 1.3.2.3.2 for category 2 and table of sub-clause 1.3.2.3.3 for category3


- Observation period of one week in fixed steps of 10 minutes.

- Determination of the number of 10 minutes intervals during which:

- the supply voltage is within 15 % of its nominal voltage: N

- the supply voltage differs by more than 10% from the nominal value and it is within 15 % its nominal value: N1


Nominal value: - In LV: nominal = 230 V between phase and neutral,

- In MV: declared voltage is defined by agreement.

The requirement of the standard is fulfilled if:

N1/N 5%

2.3 Rapid voltage changes: flicker severity


The instrumentation shall measure the Plt value and shall comply with IECPublication 868 - EN 60868.




23002Ren9531 July 199517



- Observation periods of one week in fixed steps of 10 minutes

- Acquisition of all Pst values (short term flicker severity measured in each 10 minutesinterval)

- Determination of valid Pst values by elimination of Pst values related to 10 minutesintervals during which the voltage is outside the range 15% of its nominal valueand/or a voltage dip with depth 15% of the nominal voltage has occurred

- Evaluation of the Plt values (long term flicker severity) on the basis of 12 validconsecutive values of Pst

- Determination of:

- number of the evaluated Plt values: N

- number of Plt exceeding 1: N1

2.3.4 Limits for compliance


N1/N 5%.

2.4 Supply voltage dips

2.4.1 Measurement

The instrumentation shall measure the r.m.s. voltage every half-cycle.


An a.c. voltage that fulfills the requirements of reference conditions is applied at theinstrumentation input; at zero crossing, the voltage shifts to a fixed value comprised between 1and 90 % of the nominal voltage in less than one half cycle. The measurement equipment hasto measure the new voltage value at the end of the first half cycle following the modification ofthe voltage magnitude (excluding the half cycle during which the voltage modification takesplace).

Any other functional arrangement giving equivalent or improved performance isacceptable.

23002Ren9531 July 199518

The instrumentation presents with respect to the nominal value an intrinsic error e r on the depth of the voltage dip less than:

- for category 1 equipment: 0,5 %,

- for category 2 equipment: 2 %,

- for category 3 equipment: given by the manufacturer.

The same process applies when returning to reference voltage.

The voltage dip is defined by a pair of data: - duration

- depth.

The duration corresponds to the period during which the r.m.s. values measuredremain less than 90 % of the declared value. The depth of a voltage dip is defined as thedifference, expressed in % of the declared voltage, between the minimum r.m.s. value duringthe voltage dip and the declared voltage.

As a consequence of the absence of measurement during a half cycle (i.e. during thevoltage changes) at the beginning and at the end of a voltage dip, voltage dips with a durationshorter than 20 ms are not measured with the required accuracy. For the same reasons, theaccuracy of the duration of a voltage dip is equal to:

20 ms

for categories 1, 2, and 3 equipment.


Indicatives values are given in EN 50160.

- Observation periods of one year for category 1 and case by case for the othercategories.

- Determination of numbers Nij (source UNIPEDE-DISDIP):

Depth (d % )/ Duration (t)

10 mst

23002Ren9531 July 199519

2.5 Short and long interruptions

2.5.1 General

Only categories 1 and 2 instrumentation are concerned by interruption measurements.

2.5.2 Measurement



An a.c. voltage that fulfills requirements of reference conditions is applied at theinstrumentation input ; at zero crossing, the voltage shifts to a fixed value comprised between0 and 1 % of the nominal voltage in less than one half cycle. The measurement equipment hasto detect the "zero" voltage at the end of the first half cycle following the modification of thevoltage magnitude (excluding the half cycle during which the voltage modification takesplace).



The evaluation of an interruption is defined by the duration of the interruption.

The duration corresponds to the period during which the r.m.s. values measuredremain less than 1 % of the declared value.

As a consequence of no measurement during a half cycle at the beginning and at theend of an interruption, interruptions with a duration shorter than 20 ms are not measured withthe required accuracy. For the same reasons, the accuracy of the duration of an interruption isequal to:

20 ms

for categories 1 and 2 equipment

23002Ren9531 July 199520


Indicatives values are given in EN 50 160.

- Observation periods of one year for category 1 and case by case for the othercategories.

- Determination of numbers Ni:

Duration ofinterruptions

Duration < 1 s 3 min > Duration 1s

Duration 3 min

Number of interruptions N1 N2 N3

The evaluation of N1, N2 and N3 could be made not only in terms of the individual events butalso by determining "equivalent interruption" as a combination of a sequence of individualevents or by neglecting interruptions shorter than a threshold value.

2.6 Temporary power frequency overvoltages between live conductors and earth

2.6.1 General

Only categories 1 and 2 instrumentation are concerned by overvoltage measurements.

2.6.2 Measurement



An a.c. voltage that fulfills requirements of reference conditions is applied at theinstrumentation input ; at zero crossing, the voltage shifts to a fixed value equal to3 times thenominal voltage in less than one half cycle. The measurement equipment has to measure thenew voltage value at the end of the first half cycle following the modification of the voltagemagnitude (excluding the half cycle during which the voltage modification takes place).


The instrumentation presents with respect to the nominal value an intrinsic error e r onthe overvoltage less than:




The evaluation of an overvoltage is defined by a pair of data:

23002Ren9531 July 199521

- duration,

- magnitude.

The duration of an overvoltage corresponds to the period during which the r.m.s.values measured remain more than 110 % of the declared value. The magnitude of anovervoltage is defined as the ratio expressed in % between the maximum value during theovervoltage and the declared value.

As a consequence of not measuring during a half cycle (i.e. during the voltagechange) at the beginning and at the end of an overvoltage, overvoltage with a duration shorterthan 20 ms are not measured with the required accuracy. For the same reasons, the accuracyof the duration of an overvoltage is equal to:

20 ms

for categories 1 and 2 equipment.


For this measurement mode, the range and the accuracy of some influence quantitiesgiven in sub-clause 1.3.2.3 Part 1 are extended. The following table gives the variation rangeand the accuracy of the concerned quantities:

Accuracy

Nature Variation range category 1 category 2

Voltage greater than 200% given by manufacturer

magnitude up to 200% 2 % 5 %

Frequency from 42.5 to 57.5 Hz 2 % given by

Harmonics(THD) 0-20 % 2 % manufacturer

23002Ren9531 July 199522


Indicatives values are given in EN 50160.

- Observation periods of one year for category 1 and case by case for othercategories.

- Determination of numbers of overvoltages Nij :

Overvoltages /

Duration "t"

t

23002Ren9531 July 199523

When a 3 phase a.c. voltage fulfilling the requirements of reference conditions andpresenting an unbalance ratio between 0 % and 5 % is applied at the input, theinstrumentation presents an intrinsic error e r less than:



Category 3 equipment are not concerned with unbalance measurements.


For this measurement mode, the range and the accuracy of one of the influencequantities given in sub-clause 1.3.2.3 Part 1 are extended. The following table gives thevariation range and the accuracy of the concerned quantity:

Nature Variation range Accuracy

Phase to ground voltage 0 - 200 % e r Harmonics (THD) 0-20 % 2e r




- the line to line supply voltage is within 15 % of its nominal voltage: N

- the unbalance 10 minutes measurement exceeds 2 % (3% in some area) and theline to line supply voltage is within 15 % of its nominal value: N1



N1/N 5%

2.9 Harmonic voltage

2.9.1 Measurement

Measurements give true r.m.s. values relative to the nominal voltage over either 3seconds or 10 minutes intervals(10) .

(10) In the case of an effective measuring time equal to 10 minutes (no gaps between measuring windows), the

10 minute r.m.s. value is the true r.m.s. value evaluated with an integrating time of 10 minutes.When the effective measuring time is less than 10 minutes (with gaps between windows), the integration timefor the evaluation of the r.m.s. value is obviously equal to the effective measuring time.The 10 minute r.m.s. value UhSh for a voltage Individual Harmonic Distortion of order h , is then given by:

23002Ren9531 July 199524


The instrumentation shall comply with the IEC Publication 1000-4-7.

When an a.c. voltage that fulfills requirements of reference conditions combined withpermanent individual harmonic voltage is applied at the instrumentation input, theinstrumentation presents an error given in IEC 1000-4-7:

- for category 1 equipment: class A,

- for category 2 equipment: class B.

Category 3 equipment are not concerned with harmonic measurements.


For this measurement mode, the ranges and the accuracy of some influence quantitiesgiven in sub-clause 1.3.2.3 Part 1 are extended according to the indications given by IEC1000-4-7.




- the supply voltage is within 15 % of its nominal value: N

- the individual harmonic 10 minutes measurements exceed the values defined inEN 50 160 and the supply voltage is within 15 % of its nominal value: N1

- the T.H.D. 10 minutes measurement is greater than 8% and the supply voltage iswithin 15 % of its nominal value: N2


( ) N/N1i

U ihVs,2

UhSh

=

=

where: N = number of 3 seconds r.m.s. values evaluated during any interval of 10 minutesUhVs,i = ith 3 seconds r.m.s. value of the harmonic voltage of order h, given by:

( ) MMk

U khU hVs /1

,2

=

=

where: M = number of samples in the effective measuring time of about 3 secondsUhk = individual harmonic voltage of order h of the kth sample (each sample is

relevant to a single calculated Fast Fourier Transform (FFT) value Ch corresponding to the chosen sampling window Tw).

The THD is then evaluated from the measured IHD values, with a similar approach.

23002Ren9531 July 199525


N1/N 5%

and N2/N 5%

2.10 Interharmonic voltage

If the measurement concerns an interhamonic with a specific frequency, thespecification of the measurement instrumentation is equal to that for harmonic components.

If the frequency range of the signal is unknown and wide, the frequency bandwidthhas to be split into several bands. The results of the measurement is in relation with thebandwidth of each band.

This phenomenon is still under consideration.

2.11 Mains signalling voltage

2.11.1 Measurement

The measurements give the mean value, not true r.m.s. value, over a fixed interval of3 seconds.


- Observation period of one day

- Determination of 3 seconds interval during which the supply voltage magnitude iswithin 15 % of its nominal value: N

- Determination of 3 seconds interval during which the average value of the signallingvoltage exceeds the curve define in EN 50 160 and the supply voltage magnitude iswithin 15 % of its nominal value: N1



N1/ N 1 %.

23002Ren9531 July 199526

PART 3: WITHSTAND AND IMMUNITY CHARACTERISTICS

3.1 Permanent monitoring

For permanent monitoring it is important that the measurement instrumentation forthe voltage characteristics is able to withstand and be immune to external electrical andmechanical stresses identical to those specified for electric energy metering.

The following specifications are accordingly taken from standards already in use inthe energy metering equipment (EN 61036), when it applies.

3.1.1 Requirements

3.1.1.1 Mechanical requirements

See sub-clause 4.2 of EN 60136

3.1.1.2 Electrical requirements

See sub-clause 4.4.1 and 4.4.5 of EN 60 136

3.1.1.3 Electromagnetic compatibility (EMC)

See sub-clause 4.5 of EN 60 136

3.1.2 Tests and test conditions

See sub-clause 5 of EN 60 136

3.1.2.1 General testing procedures


3.1.2.2 Tests of mechanical requirements


3.1.2.3 Tests of climatic influences


3.1.2.4 Test of electrical requirements


3.1.2.5 Tests for electromagnetic compatibility (EMC)


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3.1.3 Recommended test sequences

testsequence

nTest description

Sub-clause

of Part 3

1 Insulation test 3.1.2.4

1.1 Impulse voltage test

1.2 AC voltage test

2 Accuracy tests Part 2

3 Electrical requirement tests 3.1.2.4

3.1 Circuits load

3.2 Influence of temperature rise

4 Electromagnetic compatibility tests (EMC) 3.1.2.5

4.1 Radio interference measurement

4.2 Fast transient burst test

4.3 Withstand to HF electromagnetic field

4.4 Withstand to electrostatic discharges

5 Climatic tests 3.1.2.3

5.1 Dry heat test

5.2 Cold test

5.3 Damp heat cyclic test

6 Mechanical tests 3.1.2.2

6.1 Withstand to vibration

6.2 Shock test

6.3 Spring hammer test

6.4 Tests of protection against penetration of dust and water

6.5 Test of resistance to heat and fire

23002Ren9531 July 199528

3.2 Temporary surveying or general purpose investigations: general mechanicalrequirements

For these two categories of instrumentation only mechanical requirements arerecommended.

Reference is made to sub-clause 4.2.1 of EN 60136

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2000-030-0153-1