The rotor shaft of a synchronous machine can experience severe mechanical stress due to torque
pulsations during a pole-slip condition. All pole-slip protection relays currently on the market use the
impedance pole-slip protection method to detect a pole-slip.
No commercial relay currently available can predict accurately when a generator is about to experience a
damaging pole-slip. All the relays will only trip a generator after it has pole-slipped one or more times.
Severe mechanical damage could be caused to a machine after only one pole-slip. It is therefore essential
to enhance pole-slip protection relays to such an extent that it can trip a generator before it pole slips.
The proposed pole-slip protection function must predict when a generator will become unstable during a
network fault. As soon as instability is predicted, the generator must be tripped before the fault is cleared
to avoid damaging post-fault torque effects. Conventional impedance pole-slip protection methods are
are also discussed and the shortcomings of impedance pole-slip protection are investigated.
The new pole-slip protection function was designed by using PSCAD. Detailed PSCAD simulations on
different network configurations proved that the new pole-slip protection function will trip a generator
before a damaging pole-slip occurs. The new pole-slip protection function was also implemented on an
ABB REM543 multifunctional protection relay and tested on a RTDS. The concept of the new pole-slip
function was successfully demonstrated on the protection relay.
The operation of conventional impedance scheme relays was compared with the proposed pole-slip
function for different fault conditions. Although the new pole-slip protection function is more complex
than the existing impedance functions, it was concluded that similar skills are required to test and
commission the new protection function. The new pole-slip function outperforms the impedance
protection methods, since the new protection function can trip the generator before it pole-slips. / PhD (Electrical Engineering), North-West University, Potchefstroom Campus, 2011
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/9730 |
| Date | January 2011 |
| Creators | Lamont, Lafras |
| Publisher | North-West University |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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