standard 50 160
TRANSCRIPT
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......................................................................................................
Measurement guide for voltage
characteristics
......................................................................................................
Electricity product characteristics and
electromagnetic compatibility......................................................................................................
July 1995
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The Union of the Electricity Industry EURELECTRIC has been formed through a merger of the two associations
and
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1
International Union of Producers and Distributors of Electrical Energy2 European Grouping of Electricity Undertakings
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Measurement guide for voltage characteristics
............................................................................................
Electricity product characteristics and
electromagnetic compatibility
............................................................................................
Paper prepared by:
Roger OTT (FR); Gerrit BLOM (NL); Michel DUSSART (BE); Pierre
FERRAND (FR); Peter LODERER (AT)
The work has been started by Andr MENDES (FR) and was carried out
with the contribution of Jean-Louis JAVERZAC (FR), Richard NOTTELET
(FR) and Pierre PICARD (FR)
Copyright
Union of the Electricity Industry - EURELECTRIC, 2000
All rights reserved
Printed at EURELECTRIC, Brussels (Belgium)
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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 and
earth................................................................................................................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 mechanical
requirements.................................................................................................... 28
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SUMMARY
The purpose of this report is to provide a practical approach for measuring and
evaluating the characteristics of supply voltage as specified by the European standard EN
50160, issue of November 1994.
The problem has been analysed with a view of the different situations which can
occur in practice:
- permanent verification of supply characteristics, depending on contractual
obligations
- temporary surveying motivated by distributor's requirements or by user's complaints
- surveys to check the performance of a supply system for general purpose
investigations.
After having defined the reference environmental conditions and the required
operating characteristics of the measuring instruments, the report describes the measurement
methods and the information processing criteria for the evaluation of each of the voltage
characteristics considered in the European standard.
This document provides a suitable solution for the assessment of the voltage
characteristics and represents an effective contribution of UNIPEDE to the definition of a
complete frame of reference for the electricity supply service, according to the general policy
being pursued by the European Union.
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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 users
supply terminals.
To check the compliance of the actual voltage characteristics with the EN standard it
is necessary to provide more detailed information on measuring and evaluation methods.
Moreover the functional and constructive specifications for the measuring equipment
should be established with reference to the application requirements and the relevant
international 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 the
instruments 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 contractual
verifications),
- 2nd category temporary surveying (for example to check the performance of
the 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 dealing
with environmental conditions.
As far as these requirements are concerned, the report deals only with the influencing
factors which should be complied with for each category.
When some parameters are not expressly given, it is understood that they are left to
be declared by the manufacturer.
The guidelines given in the report may also be used for verification of voltage
characteristics with tolerances different from those stated in the EN 50160 Standard, by
making the necessary modifications.
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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 electrical
insulation
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 its
calibration
IEC 1036 EN 61036 Alternating current static watt-hour meter for active
energy (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 harmonics
measurements and instrumentation, for power supply
systems and equipment connected thereto
IEV 50(301) General terms on measurements in electricity
CISPR 22 EN 55022 Limits and methods of measurement of radio
interference characteristics of Information technologyequipment
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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 in
low-voltage supply systems, or accessible via measurement transformers. The instrumentation
performs the measurement of certain voltage characteristics by means of an analog, digital or
other data acquisition technique. As a last step, the measured parameters are subjected to a
conditioning which is most often meant to eliminate the effect of spurious phenomena and
processed for evaluation.
This principle is illustrated by the following figure.
Measurement
transformersMeasurement
unitEvaluation 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 between
the voltage supplied and the measurement evaluation. For the purpose of this guide the term
"measurement instrumentation" will be restricted to the blocks "measurement unit and
evaluation unit". In particular, the requirements dealing with accuracy will only apply to these
units, 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 normal
operating conditions, so that when making evaluations it is to be intended that any time
interval 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
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include the characteristics of the measured voltage given by CENELEC standard EN 50 160 in
addition to "external" influence quantities.
Moreover, the supply of the measurement system shall be designed in such a way that
it 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 be
specified by the equipment manufacturer of the measurement.
The connection devices of "voltage" circuits must comply with safety rules and with
related regulations.
1.3.2.2 Reference conditions
Definition of influence quantity Any quantity, generally external to the measurement
equipment, which may affect its working performance (
IEV 301-08-09 modified).
Definition of reference conditions Appropriate set of influence quantities and performance
characteristics, with reference values, their tolerances
and reference ranges, with respect to which the intrinsic
error (r) is specified (IEV 301-08-10 modified).
The basic reference conditions (influence quantities with their reference values and
tolerance) are reported in the following table:
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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 at
the reference frequency (50 Hz)in any
direction
0 0.05 mT(1)
External electric field at reference
frequency (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.
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1.3.2.3 Specified operating range
Definition of specified operating range Range of values of a single influence quantity
which forms a part of rated operating
conditions (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 % rRipple control signals 0 - 9 %
Ambient temperature -10C - + 45CHumidity 20% - 95 %
Magnetic induction of external origin at
the reference frequency (50 Hz) in any
direction
up to 0,5 mT(4)
External electric field at reference
frequency (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 r
Fast transients 2 kV (IEC 801-4) 2 rAuxiliary supply voltage see sub-clause 1.4
Air absence of corrosive atmosphere
(2)
Only valid for time measurement accuracy.(3) Only valid for polyphases measurements - see part 2.(4) IEC1036 table 14 page 45.
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The accuracy ris specified for each measurement mode (refer to Part 2).
In addition to this, for a permanent installation the measurement device shall have
immunity to mechanical and external electromagnetic stresses. These are described in Part 3.
1.3.2.3.2 Operating range for category 2.
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(5) 2 r
Unbalance 0 - 5 %
Harmonics (THD) 0 - 15 %
Interharmonics (any
frequency)
3 %
Ripple control signals 0 - 9 %
Transient overvoltages 2 kV (IEC 1000-4-5)
Auxiliary supply voltage see sub-clause 1.4
Air absence of corrosive atmosphere
(5) Only valid for time measurement accuracy.
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3.2.3.3 Operating range for category 3
Influence quantities Range Accuracy
Frequency 42,5 Hz - 57,5 Hz 2 rVoltage magnitude nominal 15% 2 r
flicker (Pst) 0 - 4
Unbalance 0 - 5 %
Harmonics (THD) 0 - 15 % 4 r
Interharmonics (at every
frequency)
3 %
Ripple control signals 0 - 9 %
Transient overvoltage 0,5 kV (IEC 1000-4-5)
Ambient temperature +15C, + 30C 2r
Auxiliary supply voltage see sub-clause 1.4
Air absence of corrosive atmosphere
1.3.2.4 Limit range of operation
Definition of limit range of operation Extreme conditions which an operating
measurement equipment can withstand without
damage and without degradation of its
metrological characteristics when it is
subsequently operated under its rated operating
condition (3.6.10 IEC 1036).
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1.3.2.4.1 Limits for category 1
Influence quantities Range
Voltage magnitude 0 to 1.25 Unominal
Ambient temperature -20C, + 55C
Humidity 10% - 100 %
Auxiliary supply voltage see sub-clause 1.4
Transient overvoltages 9 kV (IEC 1000-4-5)
Air absence of corrosive
atmosphere
Electromagnetic influence quantities are given in Part 3.
1.3.2.4.2 Limits for categories 2
Influence quantities Range
Auxiliary supply voltage see sub-clause 1.4
Transient overvoltages 2 kV (IEC 1000-4-5)
1.3.2.4.3 limits for categories 3
Influence quantities Range
Auxiliary supply voltage see sub-clause 1.4
Transient overvoltages 0.5 kV (IEC 1000-4-5)
1.3.2.5 Storage and transportation conditions
Definition of storage and transportation
conditions
Extreme conditions which a non-operating
measurement equipment can withstand without
damage and without degradation of its
metrological characteristics when it is
subsequently operated under its rated operating
condition (3.6.11 IEC 1036).
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1.3.2.5.1 Conditions for category 1
Influence quantities Range
Ambient temperature -25C, + 70C
Humidity 10% - 100 %
Air absence of corrosive atmosphere
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 auxiliary
supply interruptions.
The magnitude and two different durations of the interruption of the auxiliary supply
voltage interruption are considered:
- t1: duration during which the measurement equipment continues its normal
operating 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
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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 of
voltages directly applied to the instrumentation shall be the image of the voltages delivered by
the distributor (phase-phase or phase-neutral voltages).
If, for cost reasons for instance, the measurement is made at the supply transformer
secondary terminal, the voltage characteristics are not exactly the same as at the transformer
primary. The interpretation of the measurement results is delicate and is not dealt with in the
present 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 the
characteristics 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 standardised
and 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 VA
in all cases. The accuracy class is 0.5.
The accuracy of voltage transformers, in frequency range from 45 Hz to 2000 Hz is
better than 5 %.
1.5.3 Influence of existing voltage transformers
As far as these devices are concerned, before any measurement, it will be necessary to
check the compliance of their characteristics with the recommendations of IEC 186 and 186 A
and 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 of
harmonic and interharmonic voltage.
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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 be
measured.
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 their
reference 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 carried
out on the basis of the the valid samples.
A sample is considered valid if the mean value of the voltage over the applicable
specified basic fixed time interval, measured as stated at sub-clause 2.2.1, remains within the
range 15 % of the supply nominal (or declared) voltage.
The basic fixed time intervals used in the different measurement modes are the
following:
- 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 following
approach 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 the
15 % tolerance): Nnonvalid
- Number of valid 10-minute intervals (intervals with mean voltage within the 15 %
tolerance): 1008-N
nonvalid
= N
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- 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 errorr:
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 the
concerned 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 of
sub-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 supply
voltage is within 15 % of its nominal value: N1
(6) Mean arithmetic value over a then minutes time period.
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- the frequency differs by more than - 3 Hz, + 2 Hz from the nominal value and the
supply voltage is within 15 % of its nominal value: N2
2.1.5 Nominal value and limits for compliance
Nominal value:
fn = 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 measurement
value is the mean value over a fixed 10 minutes time period. Every measurement updates
previous one at the end of the 10 minutes period.
2.2.2 Specification of the instrumentation
When an a.c. voltage that fulfills requirements of reference conditions is applied at the
instrumentation input, the instrumentation presents with respect to the nominal value an
intrinsic errorr 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
tdtuTU 0
2
)()(
1. T is equal to a
period time (according to IEC definition).
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2.2.3 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 the
concerned 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 of sub-clause 1.3.2.3.2 for category 2 and table of sub-clause 1.3.2.3.3 for category
3
2.2.4 Measurement evaluation
- 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
2.2.5 Nominal value and limits for compliance
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
2.3.1 Specification of the instrumentation
The instrumentation shall measure the Plt value and shall comply with IEC
Publication 868 - EN 60868.
2.3.2 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 the
concerned quantity:
Nature Variation range
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Harmonics (THD) 0 - 20 %
2.3.3 Measurement evaluation
- Observation periods of one week in fixed steps of 10 minutes
- Acquisition of all Pst values (short term flicker severity measured in each 10 minutes
interval)
- Determination of valid Pst values by elimination of Pst values related to 10 minutes
intervals during which the voltage is outside the range 15% of its nominal value
and/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 valid
consecutive values of Pst
- Determination of:
- number of the evaluated Plt values: N
- number of Plt exceeding 1: N1
2.3.4 Limits for compliance
The requirement of the standard is fulfilled if:
N1/N 5%.
2.4 Supply voltage dips
2.4.1 Measurement
The instrumentation shall measure the r.m.s. voltage every half-cycle.
2.4.2 Specification of the instrumentation
An a.c. voltage that fulfills the requirements of reference conditions is applied at the
instrumentation 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 has
to measure the new voltage value at the end of the first half cycle following the modification of
the voltage magnitude (excluding the half cycle during which the voltage modification takes
place).
Any other functional arrangement giving equivalent or improved performance is
acceptable.
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The instrumentation presents with respect to the nominal value an intrinsic error ron 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 measured
remain less than 90 % of the declared value. The depth of a voltage dip is defined as the
difference, expressed in % of the declared voltage, between the minimum r.m.s. value during
the voltage dip and the declared voltage.
As a consequence of the absence of measurement during a half cycle (i.e. during the
voltage changes) at the beginning and at the end of a voltage dip, voltage dips with a duration
shorter than 20 ms are not measured with the required accuracy. For the same reasons, the
accuracy of the duration of a voltage dip is equal to:
20 ms
for categories 1, 2, and 3 equipment.
2.4.3 Measurement evaluation
Indicatives values are given in EN 50160.
- Observation periods of one year for category 1 and case by case for the other
categories.
- Determination of numbers Nij (source UNIPEDE-DISDIP):
Depth (d % )
/ Duration (t)
10 mst
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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
The instrumentation shall measure the r.m.s. voltage every half-cycle.
2.5.3 Specification of the instrumentation
An a.c. voltage that fulfills requirements of reference conditions is applied at the
instrumentation input ; at zero crossing, the voltage shifts to a fixed value comprised between
0 and 1 % of the nominal voltage in less than one half cycle. The measurement equipment has
to 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 takes
place).
Any other functional arrangement giving equivalent or improved performance is
acceptable.
The same process applies when returning to reference voltage.
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 measured
remain less than 1 % of the declared value.
As a consequence of no measurement during a half cycle at the beginning and at the
end of an interruption, interruptions with a duration shorter than 20 ms are not measured with
the required accuracy. For the same reasons, the accuracy of the duration of an interruption is
equal to:
20 ms
for categories 1 and 2 equipment
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2.5.4 Measurement evaluation
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 of
interruptions
Duration < 1 s 3 min > Duration 1
s
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 but
also by determining "equivalent interruption" as a combination of a sequence of individual
events 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
The instrumentation shall measure the r.m.s. voltage every half-cycle.
2.6.3 Specification of the instrumentation
An a.c. voltage that fulfills requirements of reference conditions is applied at the
instrumentation 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 the
new voltage value at the end of the first half cycle following the modification of the voltage
magnitude (excluding the half cycle during which the voltage modification takes place).
Any other functional arrangement giving equivalent or improved performance is
acceptable.
The instrumentation presents with respect to the nominal value an intrinsic errorronthe overvoltage less than:
- for category 1 equipment: 0,5 %,
- for category 2 equipment: 2 %.
The same process applies when returning to reference voltage.
The evaluation of an overvoltage is defined by a pair of data:
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- 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 an
overvoltage is defined as the ratio expressed in % between the maximum value during the
overvoltage and the declared value.
As a consequence of not measuring during a half cycle (i.e. during the voltage
change) at the beginning and at the end of an overvoltage, overvoltage with a duration shorter
than 20 ms are not measured with the required accuracy. For the same reasons, the accuracy
of the duration of an overvoltage is equal to:
20 ms
for categories 1 and 2 equipment.
2.6.4 Influence quantities at the specified operating range
For this measurement mode, the range and the accuracy of some influence quantities
given in sub-clause 1.3.2.3 Part 1 are extended. The following table gives the variation range
and 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
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2.6.5 Measurement evaluation
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
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When a 3 phase a.c. voltage fulfilling the requirements of reference conditions and
presenting an unbalance ratio between 0 % and 5 % is applied at the input, the
instrumentation presents an intrinsic errorrless than:
- for category 1 equipment: 0,2 %,
- for category 2 equipment: 1 %.
Category 3 equipment are not concerned with unbalance measurements.
2.8.3 Influence quantities at the specified operating range
For this measurement mode, the range and the accuracy of one of the influence
quantities given in sub-clause 1.3.2.3 Part 1 are extended. The following table gives the
variation range and the accuracy of the concerned quantity:
Nature Variation range Accuracy
Phase to ground voltage 0 - 200 % r
Harmonics (THD) 0-20 % 2r
2.8.4 Measurement evaluation
- Observation period of one week in fixed steps of 10 minutes.
- Determination of the number of 10 minutes intervals during which:
- 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 the
line to line supply voltage is within 15 % of its nominal value: N1
2.8.5 Limits for compliance
The requirement of the standard is fulfilled if:
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 3
seconds 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:
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2.9.2 Specification of the instrumentation
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, the
instrumentation 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.
2.9.3 Influence quantities at the specified operating range
For this measurement mode, the ranges and the accuracy of some influence quantities
given in sub-clause 1.3.2.3 Part 1 are extended according to the indications given by IEC
1000-4-7.
2.9.4 Measurement evaluation
- 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 value: N
- the individual harmonic 10 minutes measurements exceed the values defined in
EN 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 is
within 15 % of its nominal value: N2
2.9.5 Nominal value and limits for compliance
( ) N/N
1iU ihVs,
2UhSh
=
=
where: N = number of 3 seconds r.m.s. values evaluated during any interval of 10 minutes
UhVs,i = ith 3 seconds r.m.s. value of the harmonic voltage of order h, given by:
( ) MM
k
U khUhVs /
1,
2
=
=
where: M = number of samples in the effective measuring time of about 3 seconds
Uhk = individual harmonic voltage of order h of the kth sample (each sample is
relevant to a single calculated Fast Fourier Transform (FFT) value Chcorresponding to the chosen sampling window Tw).
The THD is then evaluated from the measured IHD values, with a similar approach.
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The requirement of the standard is fulfilled if:
N1/N 5%
and N2/N 5%
2.10 Interharmonic voltage
If the measurement concerns an interhamonic with a specific frequency, the
specification of the measurement instrumentation is equal to that for harmonic components.
If the frequency range of the signal is unknown and wide, the frequency bandwidth
has to be split into several bands. The results of the measurement is in relation with the
bandwidth 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 of
3 seconds.
2.11.2 Measurement evaluation
- Observation period of one day
- Determination of 3 seconds interval during which the supply voltage magnitude is
within
15 % of its nominal value: N
- Determination of 3 seconds interval during which the average value of the signalling
voltage exceeds the curve define in EN 50 160 and the supply voltage magnitude is
within 15 % of its nominal value: N1
2.11.3 Limits for compliance
The requirement of the standard is fulfilled if:
N1/ N 1 %.
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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 and
mechanical stresses identical to those specified for electric energy metering.
The following specifications are accordingly taken from standards already in use in
the 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
See sub-clause 5.1 of EN 60 136
3.1.2.2 Tests of mechanical requirements
See sub-clause 5.2 of EN 60 136
3.1.2.3 Tests of climatic influences
See sub-clause 5.3 of EN 60 136
3.1.2.4 Test of electrical requirements
See sub-clause 5.4 of EN 60 136
3.1.2.5 Tests for electromagnetic compatibility (EMC)
See sub-clause 5.5 of EN 60 136
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3.1.3 Recommended test sequences
test
sequence
n
Test 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
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3.2 Temporary surveying or general purpose investigations: general mechanical
requirements
For these two categories of instrumentation only mechanical requirements are
recommended.
Reference is made to sub-clause 4.2.1 of EN 60136
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