Development and testing of 1100 kV GIS HOLAUS Walter, RIECHERT Uwe, SOLOGUREN Diego, KRÜSI Urs ABB Switzerland Ltd. ELK-5 equipment at ”Jingmen” substation IEC/CIGRE UHV Symposium, New Dehli 29.-30.01.2009

Development of UHV GIS: Environment Only a few potential markets worldwide e.g. China, India, .. Huge development effort for a limited number of customers Chinese market supplied by local suppliers International standards (so far) do not cover 1100 kV AC Development is based on customer specification Limited possibilities to test 1100 kV GIS equipment Only a few test labs worldwide are equipped for UHV testing Test items and test poles tend to be huge -> transport & space limitations Rated power of one UHV GIS bay is 6‘9 GW Robustness is key factor for UHV GIS and other components Substation layouts to support high availability ABB finished UHV GIS development and type testing in 2008 Equipment assembled by Xian Shiky in China Equipment is installed and in operation at “Jingmen” substation

ELK-5 GIS: Main ratings Um 1100 kV System Voltage 1000 kV Rated lightning impulse withstand level 2400 kV Rated short-duration pfwv to ground 1100 kV, 1 min Rated short-duration pfwv across isol. distance 1100 + 635 kV Rated lightning impulse wv. across open gap 2400 + 900 kV Rated switching impulse wv. to ground 1800 kV Rated switching impulse wv. across open gap 1675 + 900 kV Rated frequency 50 Hz Rated normal current for feeder circuits 4000 A Rated normal current for main busbar circuits 8000 A Rated short time withstand current 50 kA, 3s Rated peak withstand current 125 kA Partial discharge level of each GIS component <3pC at Um/3

Layout proposal for Hybrid GIS, 2 CB layout BB1 15 m Exit 18.5 m BB2 Top view 1 phase: DES CT CB CB drive Closing resistor

Layout characteristics All GIS equipment close to floor level “Hook” shape compensates elongations All drives placed within 1.5 m height Density sensors close to floor level No platforms required for GIS installation CB drive and CB tank can be removed without disassembling other GIS parts Only small steel structures required Biggest transport unit less than 8 tons Most spacers are arranged vertically

Design of 1100 kV circuit breaker Existing interrupting units applied 4 interrupter units connected in series, A high-speed switch for closing resistor One drive operating interrupters and switch Closing resistor in separate tank as an option Overall weight: 7.5 tons CB Switch R 9300 mm Drive Circuit breaker: 4 interrupters Linkage CO switch Closing resistor

Drive energy for 1100 kV circuit breaker Calculation of drive energy i1 i2 i3 ix Result 4 interrupting units connected in series require the least drive energy for 1100 kV Using less interrupting units increases opening speed and drive energy demand

Thermal dimensioning of closing resistor Example: Assumptions for simulation Results for this simulation 2 x Phase opposition within 30 min, 11 ms pre-insertion each Resistance value: 560 Ohm at 20°C Starting temperature 50 °C Cooling time constant: 3000 s Resistance value changes due to Temperature Voltage Dissipated Energy 91.7 MJ Temperature rise 120.3 °K Max temp of resistor discs 170.3 °C Cooling during 30 min First PO insertion Second PO insertion Resistance Ohm Energy MJ Temperature K

Size comparison ABB circuit breaker & drive 1100 kV with closing resistor 4 interrupters HMB 16 Linkage CO switch Closing resistor 550 kV with closing resistor 2 interrupters + closing resistor HMB 8 550 kV 2 interrupters HMB 8 300 kV 1 interrupter HMB 4

Size comparison ABB circuit breaker & drive 550 kV with closing resistor 2 interrupters + closing resistor HMB 8 550 kV 2 interrupters HMB 8 300 kV 1 interrupter HMB 4

Voltage grading along the 4 interrupters Static calculations Simulation circuit Voltage grading capacitance Inner: CP=2.5 nF, Outer: CP=2.7 nF Stray capacitance: CE=75.5 pF AC 50 Hz calculations Voltage grading factor: 1.056 Dynamic voltage distribution Series resistance: 25 Ohm Inductance: 500 nH Using worst-case assumptions for tolerances Specific calculations required for half-pole testing

Dielectric Type Tests AC: 1100 kV, 1 min AC-AC: 1100 + 635 kV UHV PD Sensor 1 Sensor 2 Sensor 3 Sensor 4 AC: 1100 kV, 1 min AC-AC: 1100 + 635 kV LI-AC: 2400 + 900 kV SI: 1800 kV SI-AC 1675 + 900 kV Specific remarks Lightning impulse voltage Overshoot of 7 – 10 % Combined voltages Overcoupling of 20 % PD measurement Background noise level of 7 pC at 1000 kV Non-conventional PD measurement methods (UHF)

Power tests on UHV Circuit breaker Breaking and switching tests at XIHARI lab as half-pole tests Two interrupters under test The other two breaks act as auxiliary breaker. T100a and T100s additionally as full-pole tests TRV voltages at both sides of the circuit breaker The enclosure was connected to one side TRV

Examples: TRV’s from power testing T100a Major loop Half pole test T60a Half pole test Voltage Time [ms] Voltage Time [ms]

Making Tests T100s(a) Laboratories have synthetic making circuits capable to ignite 550 kV CB For longest pre-striking arc in the 1100 kV breaker, SF6 pressure was reduced to 0.2 MPa The pre-arcing time of the 1100 kV circuit breaker with four breaks was similar to the pre-arcing time of a 550 kV circuit breaker with two breaks of the same design. Advantages by reducing pressure Simple measure to perform a making test without having the full making voltage available. Multiple making operations without disassembly Correct mechanical forces for the drive Correct pre-arcing distance

Design of TV5 disconnector Designed as 90 ° angle disconnector Existing DES drive from ABB 550 kV applied No linkage between the three phases No VFT resistor applied VFT calculations show, that VFT resistor is not required. VFT levels remain below 2.2 pu. BIL levels is 2.6 pu. This provides margins for VFT stress. Enclosure as welded construction Contact area optimized for improved bus transfer switching capability Earthing switch as an option Simple design with small number of parts Moving contact Fixed contact Drive Insulator Insulator Active parts of disconnector

UHV Disconnector switching tests at STRI lab Test set-up for disconnector switching tests in STRI, Ludvika, Sweden Test circuit TD2 TD1, TD2, TD3 tests performed Huge effort for testing Max. VFT peaks of 2.23 pu measured Confirmed simulations Average arcing time 280 ms at TD2

Conclusions UHV GIS equipment rated 1100 kV, 4/8 kA, 50 kA has been designed and fully type tested Design of the UHV GIS components has been done for optimum layouts and flexibility in GIS or hybrid GIS substations Energization done in 12/2008 at Jingmen substation in China Although test laboratories have invested in facilities for testing at UHV voltage levels, type testing remains a very challenging task