Special Requirements of IEEE C37.013 for Generator Circuit ... · PDF fileGenerator Circuit...

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November 20, 2009

Sector Energy, Business Unit Medium Voltage© Siemens AG 2009

Special Requirements of IEEE C37.013 for Generator Circuit BreakerApplications

Sector Energy, Business Unit Medium Voltage

© Siemens AG 2009November 09Folie 2

Generator Circuit Breaker Applications

What is different about generator circuit breakers?

Applicable standards Special considerations Vacuum versus SF6 technology Questions.



Generator and Distribution Circuit Breakers

Generator circuit breaker Distribution circuit breaker



Circuit Breakers for DistributionRequirements

Standards:IEEE C37.04 Rating structure for HV circuit breakersIEEE C37.09 Tests for HV circuit breakersIEEE C37.10 Application guide for HV circuit breakers.

X/R ratio: 17 (60 Hz).

Time constant of dc decay: 45 ms.

TRV typical values (15 kV, class S1 cable):Peak voltage (uc) = 25.7 kVTime-to-peak (t3) = 66 µsRRRV 0.39 kV/µs.

Duty cycle: O – t’ – CO – t – CO t’ = 0.3 s for reclosing / 15 s for non-reclosing

t = 3 minutes.



Circuit Breakers for GenerationRequirements

Standards:IEEE C37.013 Generator circuit breaker.

X/R ratio: 50 (60 Hz).

Time constant of dc decay: 133 ms.

TRV typical values (15 kV, 100 MVA machine):Peak voltage (E2) = 1.84 V = 1.84 x 15.0 = 27.6 kVTime-to-peak (T2) = 0.62 V = 0.62 x 15.0 = 9.3 µsRRRV 3.5 kV/µs.

Duty cycle: CO – 30 min – CO.



IEEEC37.04 for distribution circuit breakers expresses TRV in terms harmonized with IEC with peak voltage uc, and time-to-peak t3.

IEEE C37.013 still uses old TRV expressions with peak voltage E2 and time-to-peak T2. Peak voltage is not changed, but t3 is approximately 0.88 x T2.

The physics are not changed, just the representation.

Notes on TRV Representation



IEEE C37.04-1999 Scope

IEEE Standard Rating Structure for AC High-Voltage Circuit Breakers

1. Scope

This standard establishes a symmetrical current rating structure and construction requirements for all indoor and outdoor types of ac high-voltage circuit breakers rated above 1000 V. It is only applicable to three-pole circuit breakers used in three-phase systems and single-pole circuit breakers used in single-phase systems.

This standard does not cover circuit breakers used at frequencies other than 50 Hz or 60 Hz, or generator circuit breakers that are covered in IEEE Standard C37.013-1997.



IEEE C37.013-1997 Scope

IEEE Standard for AC High-Voltage Generator Circuit Breakers Rated on a Symmetrical Current Basis

1. Scope

This standard applies to all ac high-voltage generator circuit breakers rated on a symmetrical current basis that are installed between the generator and the transformer terminals...

Note: Since no other national or international standard on generator circuit breakers exists, this standard is used worldwide.



IEEE C37.013 – the International Standard for Generator Circuit Breakers

IEEE C37.013 Revision PAR (Project) PAR approved by IEEE-SA

Standards Board, March, 2009 Joint development with IEC SC 17A

(HV Switchgear and Controlgear) IEEE WG chair is convenor (WG chair) of

IEC working group.

IEC has no standard for a generator circuit breaker. The IEEE and IEC intent has been that IEEE C37.013 would be the global standard.

IEC SC 17A WG 52 WG scope: Joint IEC/IEEE revision of

IEEE C37.013: IEEE Standard for AC High- Voltage Generator Circuit Breakers Rated on a Symmetrical Current Basis



X/R = 17, τ = 45 ms X/R = 50, τ = 133 ms

X/R Ratio Determines %dc Component

%dc vs Contact Part for X/R = 17 and X/R = 50

0.0

20.0

40.0

60.0

80.0

100.0

120.0

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Contact Part time (ms)

%dc

Com

pone

nt

X/R = 17X/R = 50



X/R Ratio Effect on Asymmetrical InterruptingX/R Ratio Effect on Asymmetrical Interrupting

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.000

180

360

540

720

900

1080

1260

1440

1620

1800

1980

2160

2340

2520

2700

2880

3060

3240

3420

3600

Time (in degrees)

Cur

rent

(Isc

= 1

.00)

Instantaneous (total) current

dc component

S-factor (C37.04-1979)

dc component (in decimal form) (multiply by 100 for %dc component) (C37.04-1999)

Symmetrical current (ac component)



X/R Ratio Effect on Asymmetrical Interrupting

S factor (from IEEE C37.04-1979)Ratio of rms asymmetrical current to rms symmetrical current

Assume contact part time of 55 ms, and 50 kA symmetrical current

X/R = 17 %dc = 29.5 S = 1.084 I = 54.2 kA

X/R = 50 %dc = 66.1 S = 1.369 I = 68.5 kAover 26% higher

)100/(%21 dcI

IS

lsymmetrica

total +==



Short-Circuit Currents

Consider system shown:

Transformer1,000 A full load (self-cooled)impedance = 10%

Generator1,000 A full loadXd’’ (subtransient reactance) = 20%

For fault at F2, circuit breaker sees transformer fault current, roughly 1,000 A / 0.10 = 10 kA

For fault at F1, circuit breaker sees generator fault current, roughly 1,000 A / 0.20 = 5 kA

Note: Fault current for generator source fault is only about 50% of fault current for system (transformer) source fault

F1

F2

G



Generator Circuit Breaker Ratings

32.24.5 / 4.5 / 4.51.4 / 1.8 / 1.8

27.63.5 / 4.51.6 / 1.8

kVkV/µskV/µs

TRV parameters Peak voltage (1.84 V) RRRV transformer source RRRV generator source

30 / 30 / 3040 / 30msDelayed current zero*

75 / 65 / 6573 / 61%%dc component

50 / 63 / 7225 / 31.5 / 36

40 / 6320 / 31.5

kAkA

Short-circuit current Transformer source Generator source

50 / 11038 / 95kV/kVDielectric 60 Hz / BIL

17.515.0kVMaximum voltage

Fixed-Mounted

Drawout (Metal-Clad)

UnitCharacteristic

* Higher values may be available



Generator Circuit Breakers



Out-of-Phase Switching

Circuit Breakers for Standard Applications:

IEEE C37.04 (clause 5.12):

Out-of-phase switching is optional, not required for general purpose circuit breakersIf a rating is assigned, the preferred rating is 25% of the rated symmetrical interrupting rating, with recovery voltage of (250% rated voltage / 1.732).Therefore, out-of-phase ratings are not typically assigned to general purpose circuit breakers rated per IEEE C37.04 and tested to IEEE C37.09.



Out-of-Phase Switching

Circuit Breakers for Generator Switching Applications:

IEEE C37.013 (clause 6.2.9):

Out-of-phase switching is optional, not required for generator circuit breakersIf a rating is assigned, the assigned rating is shall be 50% of the rated symmetrical interrupting rating (transformer or system source).Out-of-phase switching recovery voltage values are based on a maximum out-of-phase condition of 90 degrees between generator and system. This is reasonable as more extreme angles would result in damage to the machine.The likelihood of out-of-phase switching is influenced by generator inertia, i.e., low-inertia machines are more likely to be subject to out-of-phase switching conditions. Generator circuit breakers should have an assigned out-of-phase switching rating.



Other Differences

Reclosing:Reclosing duty not required for generator circuit breakers.

Short-time current duration:Normal circuit breakers

3 seconds (metal-clad switchgear = 2 seconds)Generator circuit breakers

1.0 second (typically test to 3 seconds).

Closing & latching rating:Normal circuit breakers

Peak current 260% of symmetrical short-circuit (60 Hz)With X/R = 17, “real” peak is 259.3%

Generator circuit breakersPeak current 274% of symmetrical short-circuit (60 Hz)With X/R = 50, “real” peak is 274.2%.



Delayed Current Zero Example – C37.013

-4.000

-3.500

-3.000

-2.500

-2.000

-1.500

-1.000

-0.500

0.000

0.5000 10 20 30 40 50 60 70 80 90 10

0

110

120

130

140

150

160

Time (ms)

Curr

ent (

uniti

zed)



Delayed Zero Test Example

20.6 ms 30.0 ms

40.1 ms 57.7 ms



Generator Circuit Breaker Technologies

VacuumWell-suited to smaller units (up to 6,000 A or so)

Most economic for small units

Derived from proven distribution unit operators and interrupters

High experience-base

Very low arc voltage (20 - 50 V)Little affect on X/R ratioLower arc voltage = less arc energy = lower contact erosion

Extremely rapid recovery of dielectric strength between contacts after interruption – good for extreme TRV levels

SF6Only option for very large units

VERY expensive

Unlike distribution products

Lower experience-base

SF6 low arc voltage (several 100 V)Somewhat higher impact on X/R ratioHigher arc voltage = higher arc energy = greater contact erosion

Less able to cope with high TRV levels

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