Muhimman abubuwa a cikin binciken kimiyya a gas insulated switchgear (GIS) na tsari da takalmi da yawa
Muhimman abubuwan da ke fiye a tattalin arziki a gas-insulated switchgear (GIS) na tsakiyar karamin hanyar
Tattalin Arziki a Gas-Insulated Switchgear (GIS)
A lokacin da mukarfi na arzikin ya ba da takamfi mai yawa na GIS da ya tabbatar da shi da ya bayyana cikakken ayyukan masu muhimmanci, yawancin tattalin da suka dace da aspekta aikinsa, wanda kuma lalace da tasirin gida da inganta, za a yi.
An ruwaito tattalin arziki masu muhimmanci haka:
1. Transient Recovery Voltage (TRV) Conditions
Yanar gizo na arziki ya zama da ita ce ake yi TRV study. Wannan tattalin tana da ma'adani ga matsayin kananan-karshe da ke faruwa da recovery voltage (RRRV) da kuma tsari na mafi girma a bangaren circuit breakers, ana yi amsa da rarrabe na aikin da ke cikin GIS. An bukata TRV values da aka faɗa ta hanyar test report da circuit breaker da kuma TRV envelopes da ake samu a industry standards.
TRV da ke faruwa a bangaren circuit breaker shine voltage across its terminals after current interruption. Shape of the TRV waveform tana da iya a kan characteristics of the electrical network around the circuit breaker. Generally, TRV stress on a circuit breaker tana da muhimmanci game da fault location, magnitude of the fault current, and switching configuration of the switchgear.
Idan TRV tana da muhimmanci don successful current interruption, circuit breakers suna type-test in a laboratory to endure a standardized TRV. Standardized TRV tana da four-parameter envelope (two-parameter envelope for circuit breakers rated up to 100 kV). First period features a high rate of rise, followed by a subsequent period with a lower rate of rise. Slope of the first period of the TRV envelope tana da muhimmanci a matsayin RRRV. In cases where the amplitude of the short-circuit-breaking current is extremely low, two-parameter envelopes must be considered to evaluate the TRV stress on a circuit breaker.
Figure 1: TRV Curve in High-Voltage Circuit Breaker
Muhimmancin wannan tattalin shine canza worst-case RRRV da maximum crest voltage across the circuit breakers within the GIS, based on the transient response of the electrical network surrounding the switchgear.
Don bayanai masu daidai game da TRV, zaka iya duba wannan article.
2. Very Fast Transient (VFT) Conditions
Yanar gizo na arziki ya zama da ita ce ake yi VFT study. A gas-insulated switchgear (GIS), very fast transient (VFT) overvoltages with oscillation frequencies in the MHz range can occur during disconnect switch operations. This is due to the rapid voltage collapse within a few nanoseconds and the length and coaxial design of the GIS.
In the area near the operated disconnect switch, frequencies of over 100 MHz may be generated. At locations farther inside the GIS, frequencies in the range of several MHz can be anticipated.
The frequencies and amplitudes of the VFT are determined by the length and design of the GIS. Owing to the traveling-wave nature of this phenomenon, the voltages and frequencies vary from one location to another within the GIS.
High amplitudes are likely to occur when long segments of gas-insulated buses are switched and when there are tapped buses at the source of the main bus section. If the natural frequencies of the source and the switched end of the bus are similar and the voltage difference across the disconnect switch is large, a significant voltage difference will be present during the opening of the disconnect switch. Generally, the highest amplitudes of the VFT are found on open GIS sections.
Figure 2: Example of VFTO Waveform in 750 kV GIS
Muhimmancin wannan tattalin shine canza VFT overvoltages within the GIS that are generated when energizing switchgear segments using disconnect switches. Additionally, VFT overvoltages resulting from circuit breaker switching operations should be computed.
3. Insulation Coordination Studies
Yanar gizo na arziki ya zama da ita ce ake yi insulation coordination studies. Such a study is necessary to confirm the location and quantity of GIS metal-enclosed type surge arresters, which are crucial for safeguarding the GIS equipment, any interconnected underground cable circuits, and other air-insulated equipment.
The insulation coordination study examines the overvoltage stresses present at the gas-insulated switchgear, its bays, and cables. These stresses are induced by lightning surges approaching the substation and the lines connected to it. Thus, for several specified substation configurations, including the normal operating configuration, the maximum voltage stresses within the GIS and at the bays, caused by typical lightning strokes (such as remote strokes, direct strokes to conductors, and strokes to the last towers of overhead lines), should be simulated.
The appropriate insulation coordination level should be validated by comparing the insulation levels of individual equipment with the maximum overvoltage stresses anticipated. This comparison should consider the maximum correction and safety factors as per industry standards.
4. Thermal Rating Calculations
Yanar gizo na arziki ya zama da ita ce ake yi thermal rating calculations for all equipment and devices in the main current paths. These thermal rating calculations need to be determined in line with the facility rating methodology of the user and the Regional System Operating Authority.
5. Effects of Ferro-resonance
Yanar gizo na arziki ya zama da ita ce ake yi study to ascertain whether there is a possibility of Ferro-resonance occurring in relation to the switching in and out of service of potential transformers in the GIS. The study should not only indicate the severity of the condition but also recommend mitigation measures, such as the use of tuned inductors.
6. GIS Resistance and Capacitance
Yanar gizo na arziki ya zama da ita ce ake bayar calculated and measured capacitance and resistance values for each component in the GIS. This includes, but is not limited to, bushings, bus runs, switches, and circuit breakers.
7. Seismic Calculations
Yanar gizo na arziki ya zama da ita ce ake bayar all documentation regarding seismic design testing (as specified by the manufacturer in the GIS documentation).
8. Electromagnetic Compatibility
Yanar gizo na arziki ya zama da ita ce ake yi studies on shielding and mitigation procedures to address interference with control, protection, diagnostics, and monitoring equipment.
9. Civil Engineering Aspects
Yanar gizo ya zama da ita ce ake bayar documentation for any special civil designs necessitated by specific site conditions to accommodate the GIS.
10. Grounding and Bonding
Yanar gizo na arziki ya zama da ita ce ake yi grounding studies in accordance with the current version of IEEE Standard 80. The manufacturer must ensure that the GIS equipment grounding complies with the National Electric Safety Code C2 and IEEE Standard 80.
All studies should be presented in formal reports and forwarded to the user within the specified time frame after the contract is awarded. All relevant documentation, including but not limited to calculations, curves, assumptions, graphs, and computer outputs, should be provided to support the conclusions drawn.
11. Logistics Studies
Figure 2 presents an example of a VFTO curve in a 750-kV GIS (please refer to this post).
Figure 1 depicts a transient voltage recovery curve after the final current extinction in a high-voltage circuit breaker.
