Schweitzer Engineering Laboratories SEL-587Z - Section 3: Relay Elements; Figure 3.3 B-Phase High-Impedance Element; Figure 3.4 C-Phase High-Impedance Element; Table 3.1 Differential Elements

3.3
Date Code 20020903 SEL-587Z Instruction Manual
Relay Elements
High-Impedance Protection
Figure 3.3 B-Phase High-Impedance Element.
Figure 3.4 C-Phase High-Impedance Element.
Setting
Description
Differential Element Pickups (87A1P through 87C2P)
Range: OFF, 20–800 V
The SEL-587Z has three independent, high-impedance differential elements,
each with two levels. Use differential elements 87A1, 87B1, and 87C1 for bus
protection and elements 87A2, 87B2, and 87C2 for alarms. All six settings
have the same range and are set in volts.
Tab le 3. 1 summarizes the input, setting, and output relationship of the
differential elements. All Relay Word bits are listed in Appendix C: Relay
Word Bits.
Setting
Calculation
Circuit parameters:
CT = ratio: 2000/5, type: C800, knee-point voltage: 432 V
I
F
= 50 kA (three-phase symmetrical)
R
CT
=0.82 Ω
R
LEAD
=0.6 Ω
n = total number of circuits = 5
_
+
_
+
87B1
87B2
Setting
87B1P
Setting
87B2P
87B
_
+
_
+
87C1
87C2
Setting
87C1P
Setting
87C2P
87C
Table 3.1 Differential Elements
Element Label Input Settings
Output
(Relay Word Bit)
High Impedance 87A, 87B, 87C 87A1P, 87B1P, 87C1P 87A1, 87B1, 87C1
High Impedance 87A, 87B, 87C 87A2P, 87B2P, 87C2P 87A2, 87B2, 87C2