Special Requirements of IEEE C37.013 for Generator Circuit Breaker Applications November 20, 2009 Schutzvermerk / Copyright-Vermerk Siemens AG 2009
Generator Circuit Breaker Applications What is different about generator circuit breakers? Applicable standards Special considerations Vacuum versus SF6 technology Questions. Folie 2
Generator and Distribution Circuit Breakers Generator circuit breaker Distribution circuit breaker Folie 3
Circuit Breakers for Distribution Requirements Standards: IEEE C37.04 IEEE C37.09 IEEE C37.10 X/R ratio: Time constant of dc decay: Rating structure for HV circuit breakers Tests for HV circuit breakers Application guide for HV circuit breakers. 17 (60 Hz). 45 ms. TRV typical values (15 kv, class S1 cable): Peak voltage (uc) = 25.7 kv Time-to-peak (t3) = 66 µs RRRV 0.39 kv/µs. Duty cycle: Folie 4 O t CO t CO t = 0.3 s for reclosing / 15 s for non-reclosing t = 3 minutes.
Circuit Breakers for Generation Requirements Standards: IEEE C37.013 Generator circuit breaker. X/R ratio: Time constant of dc decay: 50 (60 Hz). 133 ms. TRV typical values (15 kv, 100 MVA machine): Peak voltage (E2) = 1.84 V = 1.84 x 15.0 = 27.6 kv Time-to-peak (T2) = 0.62 V = 0.62 x 15.0 = 9.3 µs RRRV 3.5 kv/µs. Duty cycle: CO 30 min CO. Folie 5
Notes on TRV Representation 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. Folie 6
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. Folie 7
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. Folie 8
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 Folie 9
X/R Ratio Determines %dc Component X/R = 17, τ = 45 ms X/R = 50, τ = 133 ms %dc vs Contact Part for X/R = 17 and X/R = 50 120.0 100.0 %dc Component 80.0 60.0 40.0 20.0 0.0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Folie 10 Contact Part time (ms) X/R = 17 X/R = 50
X/R Ratio Effect on Asymmetrical Interrupting Current (Isc = 1.00) 3.00 2.50 2.00 1.50 1.00 0.50 0.00-0.50-1.00 Instantaneous (total) current dc component S-factor (C37.04-1979) dc component (in decimal form) (multiply by 100 for %dc component) (C37.04-1999) Folie 11-1.50-2.00 Symmetrical current (ac component) 0 180 360 540 720 900 1080 1260 1440 1620 1800 1980 2160 2340 2520 2700 2880 3060 3240 3420 3600 Time (in degrees)
X/R Ratio Effect on Asymmetrical Interrupting S = I I total symmetrical = 1+ 2(% dc /100) 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 ka over 26% higher Folie 12
Short-Circuit Currents Consider system shown: Transformer 1,000 A full load (self-cooled) impedance = 10% Generator 1,000 A full load Xd (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 G F1 F2 Note: Fault current for generator source fault is only about 50% of fault current for system (transformer) source fault Folie 13
Generator Circuit Breaker Ratings Characteristic Maximum voltage Dielectric 60 Hz / BIL Short-circuit current Transformer source Generator source %dc component Delayed current zero* TRV parameters Peak voltage (1.84 V) RRRV transformer source RRRV generator source * Higher values may be available Folie 14 Unit kv kv/kv ka ka % ms kv kv/µs kv/µs Drawout (Metal-Clad) 15.0 38 / 95 40 / 63 20 / 31.5 73 / 61 40 / 30 27.6 3.5 / 4.5 1.6 / 1.8 Fixed- Mounted 17.5 50 / 110 50 / 63 / 72 25 / 31.5 / 36 75 / 65 / 65 30 / 30 / 30 32.2 4.5 / 4.5 / 4.5 1.4 / 1.8 / 1.8
Generator Circuit Breakers Folie 15
Generator Circuit Breakers Folie 16
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 breakers If 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. Folie 17
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 breakers If 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. Folie 18
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 breakers Peak current 274% of symmetrical short-circuit (60 Hz) With X/R = 50, real peak is 274.2%. Folie 19
Delayed Current Zero Example C37.013 0.500 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 0.000-0.500-1.000 Current (unitized) -1.500-2.000-2.500-3.000-3.500-4.000 Time (ms) Folie 20
Delayed Zero Test Example 20.6 ms 30.0 ms 40.1 ms 57.7 ms Folie 21
Generator Circuit Breaker Technologies Vacuum Well-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 ratio Lower arc voltage = less arc energy = lower contact erosion SF 6 Only option for very large units VERY expensive Unlike distribution products Lower experience-base SF 6 low arc voltage (several 100 V) Somewhat higher impact on X/R ratio Higher arc voltage = higher arc energy = greater contact erosion Extremely rapid recovery of dielectric strength between contacts after interruption good for extreme TRV levels Less able to cope with high TRV levels Folie 22