Standards related to:

NB/T 10613-2021NB/T 10613-2021

NB

ENERGY INDUSTRY STANDARD OF THE

PEOPLE’S REPUBLIC OF CHINA

ICS 29.020

CCS K 04

Technical specification of power quality measurement

and evaluation for electric vehicle battery

charging/swap station

ISSUED ON: APRIL 26, 2021

IMPLEMENTED ON: JULY 26, 2021

Issued by: National Energy Administration

Table of Contents

Foreword ... 4

1 Scope ... 5

2 Normative references ... 5

3 Terms and definitions ... 6

4 Measurement items ... 8

5 Measurement methods and requirements ... 8

5.1 Selection of measurement points ... 8

5.2 Measurement equipment requirements ... 9

5.3 Measurement duration and measurement conditions ... 9

5.4 Data record ... 10

5.5 Measurement methods ... 10

6 Measurement result evaluation ... 10

6.1 Supply voltage deviation ... 10

6.2 Harmonics ... 11

6.3 Inter-harmonics ... 11

6.4 Three-phase unbalance ... 11

6.5 Voltage flicker ... 11

6.6 Rapid voltage changes ... 11

6.7 Power factor ... 11

6.8 Comprehensive index evaluation ... 12

Annex A (Informative) Schematic diagram of the connection of a typical electric

vehicle charging station or swap station to the power grid ... 13

Annex B (Normative) Measurement method for rapid voltage change ... 15

Annex C (Informative) A brief introduction to the influence of electric vehicle

charging on power quality of power supply points and the countermeasures

when it exceeds the standard ... 17

Annex D (Informative) Example of power quality comprehensive index

evaluation ... 20

Bibliography ... 27

Technical specification of power quality measurement

and evaluation for electric vehicle battery

charging/swap station

1 Scope

This Standard specifies the power quality measurement items, measurement

methods, measurement results evaluation requirements for electric vehicle

battery charging/swap station.

This Standard is applicable to the power quality measurement and evaluation

for electric vehicle battery charging/swap station powered by dedicated power

grids of 10kV and above. Electric vehicle charging stations or swap stations that

are powered by other voltage levels or not powered by the public grid can be

implemented by using this Standard as the reference.

2 Normative references

The following referenced documents are indispensable for the application of

this document. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any

amendments) applies.

GB/T 12325-2008, Power quality - Deviation of supply voltage

GB/T 12326-2008, Power quality - Voltage fluctuation and flicker

GB/T 14549-1993, Quality of electric energy supply. Harmonics in public

supply network

GB/T 15543-2008, Power quality - Three-phase voltage unbalance

GB/T 17626.30, Electromagnetic compatibility - Testing and measurement

techniques - Power quality measurement methods

GB/T 19862-2016, General requirements for monitoring equipment of power

quality

GB/T 24337-2009, Power quality - Inter-harmonics in public supply network

GB/T 29316-2012, Power quality requirements for electric vehicle

charging/battery swap infrastructure

GB/T 29317-2012, Terminology of electric vehicle charging/battery swap

infrastructure

GB 50966-2014, Code for design of electric vehicle charging station

3 Terms and definitions

For the purposes of this document, the terms and definitions defined in GB/T

29317-2012 as well as the followings apply.

3.1 electric vehicle (EV) battery charging station

a place that provides charging services for electric vehicles and consists of

three or more electric vehicle charging equipment

[Source: GB/T 29781-2013, 3.4, modified]

3.2 EV battery swap station

a place that provides battery replacement services for electric vehicles and

charges power batteries

[Source: GB/T 29317-2012, 5.2, modified]

3.3 rapid voltage change; RVC

the phenomenon of rapid transition of the voltage rms value between two

voltage steady states

NOTE 1: The characteristic indexes that characterize the rapid voltage change event

include the start time, the end time (duration), the maximum voltage change ΔUmax, and

the steady-state voltage change ΔUss.

NOTE 2: The rapid voltage changes described in this document are limited to voltage

changes under steady state conditions and do not involve voltage changes under transient

conditions.

NOTE 3: The voltage steady-state is related to the rapid voltage change threshold.

3.4 voltage steady-state

100 consecutive half-cycle voltage rms; slide by half cycle time interval; the

average value after sliding does not exceed the threshold range of rapid voltage

changes based on the average value before sliding

power grid. The measurement duration shall not be less than 24h.

NOTE: The measurement duration can be adjusted according to the change cycle of the

actual load size of the charging station or swap station.

5.4 Data record

The measurement data and its recording interval are as follows:

a) Supply voltage deviation, harmonics, unbalance, power factor

measurement data recording time interval include 1min, 3min, 5min or

10min. It is advisable to use 1min;

b) The long-term voltage flicker value shall be continuously recorded and

stored a set of data every 2h;

c) For the captured rapid voltage change events, the characteristic values

are recorded, including the start time, duration, maximum voltage change

ΔUmax and steady-state voltage change ΔUss.

5.5 Measurement methods

5.5.1 The measurement methods of power supply voltage deviation, harmonics,

inter-harmonics, three-phase unbalance and voltage flicker shall comply with

the requirements of GB/T 12325-2008, GB/T 14549-1993, GB/T 24337-2009,

GB/T 15543-2008 and GB/T 12326-2008 respectively.

5.5.2 The rapid voltage change measurement method is carried out in

accordance with Annex B.

5.5.3 The power factor correlation measurement method is as follows:

a) For the voltage and current measurement methods in the power factor

measurement process, see the power supply voltage class A

measurement method in GB/T 17626.30;

b) Conduct simultaneous calculation of active power, reactive power and

power factor.

6 Measurement result evaluation

6.1 Supply voltage deviation

Give the maximum value of positive and negative voltage deviations. Evaluate

whether the measurement results of power supply voltage deviation meet the

limit requirements of GB/T 12325-2008.

6.2 Harmonics

Give the total harmonic voltage distortion rate, the 2~50th harmonic voltage

content rate, and the 95% probability maximum value of the 2~50th harmonic

current. Evaluate whether the harmonic voltage content rate and the

measurement results of the harmonic current injected into the power supply

point meet the limit requirements of GB/T 14549-1993.

6.3 Inter-harmonics

Give the 95% probability maximum value of the inter-harmonic voltage content

rate in the frequency range of 0Hz~800Hz. Evaluate whether it meets the limit

requirements of GB/T 24337-2009.

6.4 Three-phase unbalance

Give the three-phase voltage unbalance, 95% probability maximum value and

maximum value of negative sequence current. Evaluate whether the three-

phase voltage unbalance and the negative sequence current injected into the

power supply point meet the limit requirements of GB/T 15543-2008.

6.5 Voltage flicker

Give the maximum value of long-term voltage flicker. Evaluate whether the

voltage flicker measurement results meet the limit requirements of GB/T 12326-

2008.

6.6 Rapid voltage changes

If a rapid voltage change event is captured, the characteristic index of the rapid

voltage change event is given. Analyze the correlation with changes in charging

load.

6.7 Power factor

Give the power factor at peak charging load. Evaluate whether the power factor

at the peak of the charging load meets the level A equipment limit 0.95 specified

in GB/T 29316-2012 or 0.95 specified in GB 50966-2014.

Annex C

(Informative)

A brief introduction to the influence of electric vehicle charging on

power quality of power supply points and the countermeasures when it

exceeds the standard

C.1 Overview

The change of electric vehicle charging and swap station load presents

randomness and diversity. It is closely related to the number of charging

vehicles in the region, the type of charging vehicles (residential vehicles or

commercial vehicles, etc.), and the charging cycle (working days or holidays)

and other factors. Therefore, different types of charging facilities and basic

power supply facilities shall be built according to different charging needs.

Reasonable matching of different charging strategies can reduce the impact of

the charging process on the power supply point of the power grid and promote

the coordinated development of electric vehicles and the power grid.

C.2 Impact of electric vehicle charging on power supply point

The influence of electric vehicle charging load on the power supply point is

mainly reflected in the increase in the load rate of the upper line and transformer

at the power supply point and the power quality exceeding the standard. The

increase in the load rate of lines and transformers leads to an increase in the

loss of the distribution network. It makes indirect deterioration of power quality

indexes. The non-linearity, impact and uncertainty of electric vehicle charging

load are easy to cause power quality indexes such as supply voltage and

harmonics to exceed the standard. It is easy to cause problems such as voltage

harmonic oscillation and voltage mutation and affect the power quality of other

users in the surrounding area. To improve the quality of electric vehicle charging

power and ensure the coordinated development of electric vehicles and power

grids, it needs to start with infrastructure, such as optimal power supply point,

increase power supply point transformer and line power supply capacity. It is

also necessary to start with the power quality control method and take

measures to reduce the impact of power quality.

C.3 Countermeasures for power quality exceeding standard

C.3.1 Supply voltage deviation

The countermeasures for the situation where the power supply voltage

deviation exceeds the standard are suggested as follows:

a) If the deviation of the operating supply voltage of the charging station or

the swap station does not meet the requirements of the national standard

limit, and the deviation of the background power supply voltage does not

exceed the standard, it is advisable to put forward measures to alleviate

the problem of voltage deviation exceeding the standard in combination

with the change of charging power, especially the change of reactive

power (see B.3.6);

b) If the deviation of the operating power supply voltage of the charging

station or the swap station does not meet the requirements of the national

standard limit, and the deviation of the power supply voltage of the

background power grid also exceeds the standard, voltage control

measures shall be taken. If necessary, the power supply lines or power

supply transformers shall be expanded and transformed to reduce the

impact.

C.3.2 Harmonics and inter-harmonics

The countermeasures for the over-standard harmonics and inter-harmonics are

suggested as follows:

a) If the harmonic voltage, inter-harmonic voltage or injected harmonic

current exceeds the standard and the background power grid harmonic

voltage or inter-harmonic voltage does not exceed the standard,

corresponding harmonic control measures shall be taken at charging and

swap stations. Or combine the relationship between harmonics and

charging power trend and adopt an orderly charging strategy;

b) If the harmonic voltage, inter-harmonic voltage or injected harmonic

current exceeds the standard and the background power grid harmonic

voltage or inter-harmonic voltage also exceeds the standard, the reasons

shall be comprehensively analyzed, and corresponding remedial

measures shall be taken.

C.3.3 Three-phase unbalance

If the three-phase voltage unbalance and the negative sequence current

injected into the power supply point exceed the standard, the charging and

auxiliary power loads in the charging and swap stations shall be reasonably

arranged according to the balance principle, or corresponding control measures

shall be taken.

C.3.4 Voltage flicker

If the voltage flicker exceeds the standard, corresponding voltage control

measures shall be taken.

a) UPQI (avg) represents the normalized average value of each item index

at the measurement point.

b) UPQI (max) represents the normalized maximum value of each item index

at the measurement point.

c) UPQI (node) represents the unified power quality index value of the

measurement point. If the measurement point harmonics, voltage flicker

and other project indexes are all less than 1 after normalization, the value

is the maximum value among the normalized values of each project index.

Otherwise, the value is 1 and gradually accumulates the part of each

exceeding index value minus 1.

d) UPQI (system) represents the unified power quality index value of a

charging and swap station system. Similar approach to single

measurement point: If the UPQI (node) value of each measurement point

is less than 1, the value is the maximum index of UPQI (node) in each

measurement point. Otherwise, the value is 1 and the remaining value

after subtracting 1 from the UPQI (node) value of each exceeding

measurement point is gradually accumulated.

e) UPQI (system/avg) represents the improved unified power quality index

value (referred to as the improved value). If the indexes of each point are

less than 1, the UPQI (system/avg) is the maximum index of the UPQI

(node) value of each measurement point. Otherwise, UPQI (system/avg)

is the average of the sum of the remaining values after subtracting 1 from

the UPQI (node) value of each over-standard point and the number of

nodes.

f) The power quality comprehensive evaluation index results of system 1 are

shown in Table D.5. When the UPQI (avg) results are all qualified, the

conclusion of the characterization measurement is wrong and unscientific.

When the UPQI (max) index value does not affect the measurement

conclusion, but the corresponding measurement point 2 and

measurement point 3 are the same, the measurement point 2 has two

indexes exceeding the standard, and the measurement point 3 has one

index exceeding the standard, it shows that the UPQI (max) index is also

unreasonable. The UPQI (node) index value can also consider the

comprehensive hazards of different indexes without affecting the

measurement conclusion. It has good applicability, so the comprehensive

evaluation index of single measurement point power quality shall use

UPQI (node) index.

Table D.5 -- Evaluation results of comprehensive indexes of system 1

power quality

...