5–40
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
The differential element for phase A will operate when:
(EQ 5.12)
where the following hold:
(EQ 5.13)
(EQ 5.14)
(EQ 5.15)
I
A
= phase current measured at the output
CT
(EQ 5.16)
I
a
= phase current measured at the neutral end
CT
(EQ 5.17)
Differential elements for phase B and phase C operate in the same manner.
FIGURE 5–4: Differential Elements
5.6.9
Ground Directional
PATH: SETPOINTS
ZV
S5 CURRENT ELEM.
ZV
GROUND DIRECTIONAL
I
operate
k I
restraint
×
>
I
operate
I
A
I
a
+
operate current
=
=
I
restraint
I
A
I
a
+
2
--------------------
restraint current
=
=
k
characteristic slope of the differential element in percent
=
k
Slope
1 if
I
R
2 CT
×
<
=
;
k
Slope
2 if
I
R
2 CT
×
≥
=
OPERATE
REGION
I
(multiples of CT)
RESTRAINT
I
(multiples
of
CT)
OPERA
TE
Slope 2 = 20%
808790A2.CDR
Slope 1 = 10%
Minimum Pickup = 0.10 x CT
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
1 GROUND
[
Z
]
DIRECTIONAL
SUPERVISE WITH
DIGITAL INPUTS: Yes
Range: Yes, No.
MESSAGE
GROUND DIRECTIONAL
MTA: 0°
Range: 0°, 90°, 180°, 270°
MTA = Maximum Torque Angle
MESSAGE
GROUND DIRECTIONAL
ALARM: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to
5
MESSAGE
GROUND DIR. ALARM
PICKUP: 0.05 x CT
Range: 0.05 to 20.00
×
CT in steps of
0.01
