Distance element polarizing logic for systems with low inertia
Bogdan Kasztenny, Mangapathirao V. Mynam · IET conference proceedings. · 2024
Mho distance protection elements operate by comparing the IZ – V operating signal with a polarizing voltage. Ideally, the polarizing voltage should have a non-zero value for all types of faults, including bolted faults close to the relay location. Therefore, preferred polarizing voltage choices include healthy phase voltages (cross-phase polarization), positive-sequence voltage (a form of cross-phase polarization), pre-fault voltage (memory polarization), or a combination thereof. Memory polarization became the prevailing form of polarizing in modern distance relays. However, memory polarization is predicated on sufficient system inertia. In systems with low-inertia generation, such as wind-powered machines and inverter-based sources, memory polarization is known to cause both security and dependability problems for distance protection. Also, memory polarization may be suboptimal in traditional power systems during power swings and in applications to series-compensated lines. This paper presents an advanced distance element polarizing logic for both low-inertia and traditional systems.