ABB KD-10 Instruction Leaflet page 8

41-490J
0.9 = The portion of the total line for which
the relay is set.
R = Current transformer ratio
C
R = Voltage transformer ratio
V
Z = Ohms per phase of the total line
pri
section
The relay tap plate setting, Z, is set according to the
following Equation:
ST
Z
= ------------- -
±
1
M
T = Compensator tap setting.
S = Auto-transformer primary tap setting.
±M = Auto-transformer secondary tap set-
ting. (This is a per unit value and is de-
termined by the sum of the values be-
tween the "L" and the "R" leads. The
sign is positive when "L" is above "R"
and acts to lower the Z setting. The
sign is negative when "R" is above "L"
and acts to raise the Z setting.)
!
The tap plate values of Tables I, II, and III are
based on standard maximum torque angle
settings.
In general recalibration of the relay to a torque
angle other than the standard value is neither de-
sirable nor required. Where it is necessary, the
phase loading potentiometers P3, P2A, or P2C
can be adjusted for other maximum torque an-
gle. The relay reach then becomes different from
the nominal tap plate settings and tap plate set-
ting should be modified as outline under Section
6.2, Maximum Torque Angle Consideration.
6.1 OBTAINING AN OPTIMUM SETTING
a. Establish Z, as per Equation 9.
b. Now refer to Table I, II, or III (page 13, page 14,
& page 15). These tables list optimum settings
for the relay.
1) Locate a table value for relay reach nearest
to the desired value Z (it will always be
within 1.5% or less off the desired value).
8
[Equ. 10]
CAUTION
Type KD-10 and KD-11 Compensator Distance Relay
2) Read off the Table "S", "T" and "M" settings.
The "M" column includes additional infor-
mation for "L" and "R" leads setting for the
specified "M" value.
3) Recheck the S, T, & M settings by using
Equation 10.
–————–—| Example 1 |———–———
Step 1 __________________________________
Assume the desired reach, Z is 7.8 ohms at 75
Step 2a _________________________________
In Table II (page 14) we find nearest value to 7.8
ohms 7.88 that is 100
desired reach.
Step 2b _________________________________
From Table II (page 14) read off:
S = 2
T = 4.06
M = +.03
and "L" lead should be connected over "R" lead, with
"L" lead connected to ".03" tap and "R" lead to tap
"0".
Step 2c _________________________________
Recheck Settings.
ST
Z = ------------- -
±
1 M
6.1.1 Checking Relay Settings Using
Reverse Procedures
Tables I, II, or III can be used to check relay settings
in the field using the following reverse procedures:
1. Read off the tap plate T, S, M settings.
2. Find corresponding Z value from appropriate ta-
bles.
6.2 MAXIMUM TORQUE ANGLE
CONSIDERATIONS
For Medium and Long Reach Relays maximum
torque angle is set at the factory for 75 degrees cur-
rent lagging voltage.
7.88
×
---------- - 101 percent of the
=
7.8
×
2 4.06
7.88
= -------------------- - =
1 + .03
°
.