Setting Guidelines - Hitachi Relion 670 Series Applications Manual

Section 7
Impedance protection
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.
7.2.3

Setting guidelines

The setting example for generator protection application shows how to calculate the most important
settings ForwardR, ForwardX, ReverseR, and ReverseX.
Table 13: An example how to calculate values for the settings ForwardR, ForwardX, ReverseR, and ReverseX
Generator
Turbine
200 MVA
(hydro)
GEN
CT 1
to OOS relay
ANSI11000090 V2 EN-US
Generator
Data required VBase = Vgen = 13.8 kV
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
calculation
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 resulted 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)
settings 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 ForwardR, ForwardX, ReverseR, and ReverseX.
• A precondition in order to be able to use the Out-of-step protection and construct a suitable lens
characteristic is that the power system in which the Out-of-step protection is installed, is modeled as
a two-machine equivalent system, or as a single machine – infinite bus equivalent power system.
Then the impedances from the position of the Out-of-step protection in the direction of the normal
load flow can be taken as forward.
• The settings ForwardX, ForwardR, ReverseX and ReverseR must, if possible, take into account, the
post-disturbance configuration of the simplified power system. This is not always easy, in particular
with islanding. But for the two machine model as in Table 13, the most probable scenario is that only
106
13.8 kV
CT 2
Unit step-up transformer
V1 = 13.8 kV
usc = 10%
V2 = 230 kV
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
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Double circuit power line
Transformer
230 kV, 300 km
300 MVA
Y
Single power line
Vline = 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)
Xline= 128.7 · (13.8/230)
Ω
Rline = 19.8 · (13.8/230)
Ω
(X and R referred to 13.8 kV)
1MRK511407-UUS Rev. N
GUID-CB86FCF6-8718-40BE-BDF2-028C24AB367D v9
Equivalent
power
system
ANSI11000090_2_en.vsd
Power system
Vnom = 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
= 0.463 Xe = 10.52 · (13.8/230)
Re = 1.05 · (13.8/230)
2
= 0.071 (X and R referred to 13.8 kV)
Phasor measurement unit RES670
Application manual
2
= 0.038 Ω
2
= 0.004 Ω