Setting Guidelines - ABB REG670 Applications Manual

Section 8
Impedance protection
8.5.3
Table 29: An example how to calculate values for the settings ForwardR, ForwardX, ReverseR, and ReverseX
Turbine Generator
(hydro) 200 MVA
CT 1
To OOS relay
IEC10000117 V2 EN
Generator
Data UBase = Ugen = 13.8 kV
required
IBase = Igen = 8367 A
Xd' = 0.2960 pu
Rs = 0.0029 pu
1-st step in ZBase = 0.9522 Ω (generator)
calculation Xd' = 0.2960 · 0.952 = 0.282 Ω
Rs = 0.0029 · 0.952 = 0.003 Ω
2-nd step in Xd' = 0.2960 · 0.952 = 0.282 Ω
calculation Rs = 0.0029 · 0.952 = 0.003 Ω
3-rd step in ForwardX = Xt + Xline + Xe = 0.064 + 0.463 + 0.038 = 0.565 Ω; ReverseX = Xd' = 0.282 Ω (all referred to gen. voltage 13.8 kV)
calculation ForwardR = Rt + Rline + Re = 0.003 + 0.071 + 0.004 = 0.078 Ω; ReverseR = Rs = 0.003 Ω (all referred to gen. voltage 13.8 kV)
Final ForwardX = 0.565/0.9522 · 100 = 59.33 in % ZBase; ReverseX = 0.282/0.9522 · 100 = 29.6 in % ZBase (all referred to 13.8 kV)
resulted ForwardR = 0.078/0.9522 · 100 = 8.19 in % ZBase; ReverseR = 0.003/0.9522 · 100 = 0.29 in % ZBase (all referred to 13.8 kV)
settings
278
slipping with severe consequences for the machines and stability of the power system.
In particular it should:
1. Remain stable for normal steady state load.
2. Distinguish between stable and unstable rotor swings.
3. Locate electrical centre of a swing.
4. Detect the first and the subsequent pole-slips.
5. Prevent stress on the circuit breaker.
6. Distinguish between generator and motor out-of-step conditions.
7. Provide information for post-disturbance analysis.

Setting guidelines

The setting example for generator protection application shows how to calculate the
most important settings ForwardR, ForwardX, ReverseR, and ReverseX.
Transformer
300 MVA
13.8 kV
CT 2
to OOS relay
Step-up transformer
U1 = 13.8 kV
U2 = 230 kV
usc = 10%
I1 = 12 551 A
Xt = 0.1000 pu (transf. ZBase)
Rt = 0.0054 pu (transf. ZBase)
ZBase (13.8 kV) = 0.6348 Ω
Xt = 0.100 · 0.6348 = 0.064 Ω
Rt = 0.0054 · 0.635 = 0.003 Ω
Xt = 0.100 · 0.6348 = 0.064 Ω
Rt = 0.0054 · 0.635 = 0.003 Ω
Settings ForwardR, ForwardX, ReverseR, and ReverseX.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Double power line
230 kV, 300 km
Single power line
Uline = 230 kV
Xline/km = 0.4289 Ω/km
Rline/km = 0.0659 Ω/km
Xline = 300 · 0.4289 = 128.7 Ω
Rline = 300 · 0.0659 = 19.8 Ω
(X and R above on 230 kV basis)
2
Xline= 128.7 · (13.8/230) =
0.463 Ω
2
Rline = 19.8 · (13.8/230) = 0.071
Ω
(X and R referred to 13.8 kV)
1MRK 502 071-UEN -
Equivalent
power
system
IEC10000117-2-en.vsd
Power system
Unom = 230 kV
SC level = 5000 MVA
SC current = 12 551 A
φ = 84.289°
Ze = 10.5801 Ω
Xe = Z · sin (φ) = 10.52 Ω
e
Re = Z · cos (φ) = 1.05 Ω
e
(Xe and Re on 230 kV basis)
2
Xe = 10.52 · (13.8/230) = 0.038
Ω
2
Re = 1.05 · (13.8/230) = 0.004 Ω
(X and R referred to 13.8 kV)
Application manual