PARTIAL DISCHARGE & TAN DELTA TESTING ON HIGH VOLTAGE CRITICAL ASSETS (6.6kV and 11kV machines)
1 DAYS TESTING COULD SAVE 12 WEEKS OF DOWN-TIME ERIKS unique approach to monitoring and maintaining your equipment can help to ensure a longer life and lower operating costs. For example our on-site Partial Discharge testing evaluates the condition of your medium/high voltage asset's insulation. (Motors, Generators, Switchgear, Transformers and Bus-bars). By repeating the tests over time ERIKS can determine any rate of deterioration, this can be monitored over time to give a more accurate assessment of when planned maintenance should be carried out to help prevent in service failure. Using our mobile test trailer, we can perform off-line tests on rotating machines - disconnected from the system - during a single day machine shutdown. With a line voltage up to 11kV and a power rating 50MW. (6.6kV and 11kVofmachines)
Thermal aging void
Coil gap
By carrying out Partial Discharge (PD) testing for electrical discharge and Tan Delta (loss Tangent) for material and gaseous leakage losses ERIKS can measure the ‘health’ of the asset, and evaluate the condition of the insulation system. Partial Discharge (PD) is an electrical discharge or spark across a void or gap in insulation between two electrodes. Voids occur in all high voltage (HV) windings. PD can accelerate damage to the insulation, which, when the insulation is sufficiently decayed, will cause the windings will fail – usually through a breakdown to earth.
For more information contact: ERIKS UK & IRELAND Distribution and Engineering Service Centre Wharf Lane Chesterfield Derbyshire S41 7NB
01246 245720 chesterfield.repair@eriks.co.uk
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VOIDS OCCUR DUE TO: Thermal deterioration over time Loose fitting coils which will be subject to vibration while the motor is running – creating wear on the insulation causing premature degradation and failure Poor quality coil insulation is prone to increased deterioration resulting in premature failure Conductive contamination – for example oil, dust particles
The Tan Delta represents the condition of the machines insulation system and indicates the leakage of electrical current to ground. Eventually when the insulation is sufficiently decayed and the discharge levels and/or leakage currents are sufficiently high the winding will fail, usually through a break down to ground. By repeating tests over time the Tan Delta curves can be trended to identify any deterioration of the winding insulation condition. Our engineering know-how, industry and application understanding enables us to identify, prevent, solve or mitigate your maintenance issues, helping you extend the product lifecycle and in turn decrease your Total Cost of Ownership, saving you time and money each and every day.
Tan delta characteristics Good low void content Poor high void content Wet and contamination
End winding phase to phase PD can occur between adjacent coils of different phases All MV/HV rotating machines will have some PD, although this is not the case for static plants as the insulation degrades the number of instances and their magnitide will increase, further eroding the insulation. Testing applications at regiular time intevals will allow the rate of deterioration to be observed, and allow ERIKS to assess the risk of failure, propose appropriate contingencies and allow maintenance and repair actions to be planned. PD testing is carried out in accordance with IEC60270 or in some instances to the customers specification.
Tan Delta
WHY CARRY OUT PD TESTING?
Wear and erosion void
TAN DELTA TESTING
0.2VL
0.4VL
0.6VL
0.8VL
1VL
Applied Voltage (VL)
Partial discharge trace
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Delamination void