Rapid Voltage Changes

Prague, 8-11 June 2009

Rapid Voltage Changes –Defintion and Minimum

Requirements

Karstein BrekkeNorwegian Water Resources and

Energy Directorate, Norway

Brekke-Norway Session 2 Paper 0789


Content

• Introduction• Existing standards• Results from a research project• Norwegian Regulation on RVC• Conclusion



Rapid Voltage Changes

• Normally categorising rapid voltage changes not exceeding ± 10% of the nominal or declared voltage level

• But how rapid is a rapid voltage change?

200

210

220

230

240

250

260

0 1 2 3 4 5 6

Time [s]

Vol

tage

[V]

253 V

207 V

∆Umax = ∆Usteady-state

200

210

220

230

240

250

260

0 1 2 3 4 5 6

Time [s]

Vol

tage

[V]

253 V

207 V

dt dv

200

210

220

230

240

250

260

0 1 2 3 4 5 6

Time [s]

Vol

tage

[V]

∆Umax

∆Usteady-state



RVC Definition in standards

• EN 50160– 3.13 rapid voltage change– single rapid variation of the r.m.s. value of a voltage between

two consecutive levels which are sustained for definite but unspecified durations (for more information see EN 61000-3-3)

• IEC 61000-4-30– 5.11 Rapid voltage changes– NOTE Clause A.4 provides some information on the

significant parameters necessary to characterize a rapid voltage change.



RVC Definition in standards

IEC 61000-3-3Defines:ΔU(t)ΔUmaxΔUsteady-state

t

10 ms

U(t)

t1 t2 t3

∆U(t)

∆Umax

∆Usteady-state



RVC in the public distribution network

• One of the most common reasons for customer complaints on power quality in Norway is caused by rapid voltage changes (RVC)

• The customers simply get annoyed by the light intensity changing often

• Most common in rural areas with low short circuit power



Motivation

• For setting requirements for RVC– Limiting annoying visible changes in the

light due to single RVCs.

• For generating a new research project– Setting requirements require that a unique

definition of RVC exists in order to ensure reliable measurements.



RVC ”Required details in definition”

• In order to ensure reliable measurements of rapid voltage changes, the following elements must be defined: 1. The steadiness of the steady state conditions; 2. The minimum duration of a steady state condition

(between two voltage change characteristics);3. The minimum rate of change (dv/dt) to consider;4. The steady state voltage change;5. The maximum voltage change during a voltage change

characteristic;6. Which voltage level to relate the change to

(i.e. the voltage before the change or the nominal voltage);7. The maximum duration of a rapid voltage change.








What elements are defined in standards?








What elements are defined in standards?

•IEC 61000-3-3: (1), 2, 4, 5 og 6.

•IEC 61000-4-30: non

•EN 50160: diffuseIn the Norwegian Quality of Supply Regulation: (1), 2, 3, 4, 5 og 6



RVC Research Project



The RVC tests in Norway• The total test carried out with 96 test persons• Two main groups of age

– Young people (16 to 26 years old)– Elderly people (65 to 80 years old)

• Two types of tests– What is visible?– What is acceptable?



The RVC tests in Norway• Tests with 60 W incandescent lamps only• No, or almost no daylight in the test rooms• Mainly RVC from 0,5 % to 5 %• Both motor start-up RVC, “ramp” RVC and

rectangular RVC



RectangularVisibility depends on voltage change

RampVisibility depends on voltage change

and duration of the change

Motor startVisibility depends on the initial peak

voltage change, the duration of voltage recovery to the new voltage level and

the voltage change from the previous to the new voltage level



Minimum duration of a steady state condition

Perception of two separate RVCs

0,97250,82150,420,550,91240,84140,390,54

Perceived as 2 RVCsTime between RVC [s]

RVC [%]



1,005 V/s5,0 %0,952 V/s5,0 %0,611 V/s5,0 %0,220,5 V/s5,0 %0,050,2 V/s5,0 %0,955 V/s4,0 %0,812 V/s4,0 %0,561 V/s4,0 %0,180,5 V/s4,0 %0,050,2 V/s4,0 %

Average visibility

dV/dt change pr sec.

Magnitude of RVC

The minimum rate of change (dv/dt) Visibility of ramp RVCs



Steadiness of the steady state condition

From the previous two slides:• dv/dt equal to or less than 0.5 % of the

nominal or declared voltage level per sec.– 0.5 % of 230V per sec equals 1.15 V/s

• In a steady state condition for at least 1 sec.• Practical measurement requires also a limit

for max/min variations in a steady state conditions



Maximum duration for RVCs

• Will indirectly be given by:– The def for the steadiness of the steady state

voltage– The minimum duration of a steady state

condition– The minimum rate of change (dv/dt)



Visibility of rectangular RVCs

0,001,007,0 %0,001,006,0 %0,001,005,0 %0,110,954,0 %0,110,843,0 %0,210,672,0 %0,220,211,0 %0,180,040,5 %

Standard deviation

Average visibility

Magnitude of RVC



Visibility of motor starts

0,981,5 s6,0 %0,790,5 s6,0 %0,861,5 s5,0 %0,680,5 s5,0 %0,711,5 s4,0 %0,520,5 s4,0 %0,541,5 s3,0 %0,350,5 s3,0 %0,321,5 s2,0 %0,210,5 s2,0 %

Average visibility

Speed up time in seconds

Initial voltage drop, ΔUmax



Norwegian regulation on RVC• A RMS voltage change within ± 10% of agreed voltage level,

which occur more rapid than 0.5 % of the agreed voltage level per second. Rapid voltage changes are expressed as the steady state and the maximum voltage changes given respectively by:

%100% ⋅Δ

=agreed

esteadystatesteadystat U

UU %100% max

max ⋅Δ

=agreedUUU

• where ΔUsteadystate is the steady state voltage change due to a voltage change characteristic, ΔUmax is the maximum voltage difference during a voltage change characteristic, and Uagreed is the agreed voltage level (i.e. the nominal or the declared).



Norwegian regulation on RVC• ”Network companies shall ensure that rapid voltage changes do not

exceed the following limits in points of connection with the respective nominal voltage value, UN [kV], for the respective frequency:

• Rapid voltage changes due to earth faults or short circuits in the network, inrush current from transformers, back feeding after faults and necessary operation couplings to uphold a satisfactory quality of supply as a whole, are not embraced by the limits in the first paragraph.”

%100% ⋅Δ

=agreed

esteadystatesteadystat U

UU

35 kV< UN0,23 kV ≤ UN ≤35 kV

1224ΔUmax ≥ 5 % 1224ΔUsteadystate ≥ 3 %

Maximum frequency pr 24 hours periodRVCs



Conclusion• A precise and unambiguous definition is necessary

for any voltage disturbance in order to achieve reliable measurements

• There exist yet no unique definition for RVCs in international standards, though the term exist

• A Norwegian research project contains results– useful for making a more unique definition for RVCs– for the visibility of RVCs as basis for limits

• The Norwegian quality regulation contains minimum requirements for RVCs and a more detailed definition in order to better ensure reliable measurements


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Rapid Voltage Changes