M. Gamlin J. Rickmann P. Schikarski R. Feger K. Feser
HIGH VOLTAGE TEST
On-Site Testing of Gas Insulated Substation with AC voltage
M. Gamlin, J. Rickmann, P. Schikarski Haefely Trench Basel, Switzerland Abstract Recent experience has proven that the reliability of a GIS/GIL can be ensured by anOn-Site AC-Testing after assembly combined with a sensitive partial discharge measurement. Either conventional 50/60 Hz transformer systems or resonant test systems with variable inductance as well as resonant test systems with variable frequency have been used to perform the GIS/GIL On-Site Testing. The paper describes the different HV test systems with their advantages and limitations and theapplicable partial discharge measuring methods. The UHF PD measuring method is emphasised. 1. Introduction R. Feger, K. Feser University of Stuttgart Germany
The TES-system can either be directly flanged to a GIS or used in combination with a SF6/Air-bushing. If directly flanged to the GIS via a multiflange housing an encapsulated coupling capacitor can be integrated. With such an arrangement andthe application of the conventional PD measuring method a PD level of less than 2 pC can be verified. An optimised design of a SF6/Air bushing in combination with a low volume intermediate flange results in an easy and short time assembly procedure. To facilitate handling and transport all encapsulated components are mounted on a base frame.
GIS/GIL testing has been performed either byACvoltage, lightning impulse voltage or switching impulse voltage or a combination of them. The experience showed that no single test method detects all fault causes with the same sensitivity. A GIS/GIL AC-testing with an increased voltage level combined with a sensitive partial discharge measurement has met best the requirements for detecting the different fault causes . Present AC test procedures ofseveral GIS/GIL suppliers consists of a prestressing at a voltage level of about (1.1-√3)Um/√3 for some seconds up to some minutes followed by the 1 minute test voltage in the range of (1.1-1.5) Um and finished by a PD measurement at a voltage level of 1.1⋅Um/√3. The AC test voltage for On-Site Testing can either be generated by a SF6 insulated test transformer system, a conventional seriesresonant test system at 50/60 Hz or a series resonant test system with variable frequency (30 .. 300 Hz). The series resonant test systems are mainly applicable for a higher test capacitance and longer test duration. 2. On Site AC Test Systems
Figure 1: 230 kV, 45 kVA test system A TES-system which is possible to be tilted hydraulically up to vertical position is designed to meet the requirements forOn-Site Testing of a GIS terminated by a SF6/Air bushing. In this case the ACtesting should be combined with an UHF PD measurement.
2.1 On Site Testing with SF6-insulated test transformer systems of the type TES SF6 insulated test transformer systems are designed for a short time duty. The max. output voltage and 15 min output power is up to 1000 kV and 375 kVA at a weight to power ratio ofapprox. 10 kg/kVA.
Figure 2: 510 kV, 105 kVA test system
2.2 On-Site Testing with conventional series resonant test systems of the insulating cylinder type RZ Conventional oil insulated series resonant reactors of the insulating cylinder type are designed for a longer test duty and higher power rating. Typical performance data of a two module tower is an output voltage up to 800 kV and a 1houtput power of up to 3200 kVA at a weight to power ratio of approx. 5 kg/kVA. The test voltage is applied to the test object via an Air/SF6 bushing. Using this design several modules can be cascaded to increase the test voltage but a fully encapsulated On-Site Test arrangement is not possible to achieve. Therefore the UHF PD measuring method is preferred when using this test arrangement. The...