ABB REG670 - Page 420

Uo
U kV
kV
Max
Ph Ph
= = =
−
3
11
3
6 35.
IECEQUATION2394 V1 EN (Equation 244)
2. One VT input is to be used in the IED. The VT ratio should be set according to the
neutral point transformer ratio. For this application, the correct primary and
secondary rating values are 6.35 kV and 110 V respectively.
3. For the base value, a generator-rated phase-to-phase voltage is to be set. Thus for
this application UBase=11 kV.
4. ROV2PTOV divides internally the set voltage base value with √3. Thus, the
internally used base is equal to the maximum Uo value. Therefore, if wanted start
is 5 percent from the neutral point, the ROV2PTOV start value is set to U1>=5%.
5. The definite time delay is set to 0.5 seconds.
ROV2PTOV application #2
ROV2PTOV is here connected to a three-phase voltage transformer set located at
generator HV terminal side.
1. Due to such connection, ROV2PTOV function calculates internally the 3Uo
voltage (that is, 3Uo=UL1+UL2+UL3) at the HV terminals of the generator.
Maximum 3Uo voltage is present for a single phase-to-earth fault at the HV
terminal of the generator and it has the maximum primary value 3Uo
Max
:
3 3 3 11 19 05Uo U kV kV
Max Ph Ph
= ⋅ = ⋅ =
−
.
IECEQUATION2395 V1 EN (Equation 245)
2. Three VT inputs are to be used in the IED. The VT ratio should be set according
to the VT ratio. For this application, the correct primary and secondary VT rating
values are 11 kV and 110 V respectively.
3. For the base value, a generator-rated phase-to-phase voltage is to be set. Thus for
this application UBase=11 kV. This base voltage value is not set directly under the
function but it is instead selected by the Global Base Value parameter.
4. ROV2PTOV divides internally the set voltage base value with √3. Thus
internally used base voltage value is 6.35 kV. This is three times smaller than the
maximum 3Uo voltage. Therefore, if the wanted start is 5 percent from the neutral
point the ROV2PTOV start value is set to U1>=3·5%=15%(i.e. three times the
desired coverage).
5. The definite time delay is set to 0.5 seconds.
ROV2PTOV application #3
ROV2PTOV is here connected to an open delta winding of the VT located at the HV
terminal side of the generator or the LV side of the unit transformer.
1. Due to such connection, ROV2PTOV measures the 3Uo voltage at generator HV
terminals. Maximum 3Uo voltage is present for a single phase-to-earth fault at the
HV terminal of the generator and it has the primary maximum value 3Uo
Max
:
Section 10 1MRK 502 071-UEN -
Voltage protection
414 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual