Method for determining the moment of closure of a circuit breaker on a high voltage line
View Patent ↗A method for determining the reclose time of a circuit breaker on a three-phase high-voltage electric network after separation of contacts 7 A, 8 A, 7 B, 8 B, 7 C, 8 C in the presence of a fault on one of the three phases A, B or C includes measuring voltages UL A0 , UL BO and UL CO , measuring voltage US AO ,determining the voltage US A0 , US B0 , and US CO , calculating the differences UL AB , UL AC and UL BC , calculating the differences US AB , US AC , and US BC . From these measurements and calculations, a determination of the reclose time is made on the basis of the voltage differences.
1. Method for determining a reclose time of a circuit breaker ( 6 ) on an electric network, said network comprising:
a high voltage source (S),
a thre-phase transmission line (L),
a circuit breaker ( 6 ) comprising at least three pairs of contacts ( 7 A, 8 A ; 7 B, 8 B; 7 C, 8 C), each pair being associated with one of the three phases (A, B C) of said line (L) and allowing an interruption of a current circulating between said source (S) and said line (L) by separating said contacts in the event of a fault on the associated phase, the first contact being on the source side and the second contact being on the line side,
a shunt compensation reactor ( 5 ) to compensate capacitive reactive power of said line (L), said reclose time being determined in the event of separation of the contacts of each pair of contacts in the presence of a fault on one of the three phases,
said determination of said reclose time being made using the following steps:
measuring a voltage (UL A0 ,UL B0 , UL C0 ) between the line side contact and ground for each of the phases,
measuring the a voltage (US A0 ) between the source side contact and ground for at least one phase,
determining a voltage (US A0 , US B0 , US C0 ) between the source side contact and ground for each of the phases,
said determination of said reclose time being characterized in that it also comprises the following steps:
calculating, for two separate phases called first and second phases, the voltage difference (UL AB , UL AC , UL BC ) between the line side contact and ground for said first phase, and the voltage difference between the line side contact and ground for said second phase, the calculation being made for each pair of separate phases,
calculating the voltage difference (US AB , US AC , US BC ) between the source side contact and ground for said first phase, and the voltage difference between the source side contact and ground for said second phase, the calculation being made for each pair of separate phases,
determining said reclose time on the basis of said voltage differences.
2. Method according to claim 1 characterized in that said determination of said reclose time (T) is made by comparing said voltage differences (US BC , UL BC ) between two healthy phases on the line side and source side.
3. Method according to claim 1 , characterized in that said determination of said reclose time (T) is made by determining the time at which the two signals corresponding to said voltage differences (US BC , UL BC ) between two healthy phases on the line side and source side are substantially equal and show the same monotony over a non
zero interval about said time.
4. Method according to claim 1 characterized in that said determination of the voltage (US A0 , US B0 , US C0 ) between the source side contact and ground for each of the phases is made by 120° and 240° phase shifting of said voltage (US A0 ) measured between the source side contact and ground for at least one phase.
5. Method to claim 1 , characterized in that said measurement of the voltage between the line side contact and ground for each phase is made using a voltage transformer ( 4 ).