GE L90 User Manual

5-286 L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
GROUPED ELEMENTS CHAPTER 5: SETTINGS
5
Igd = abs(3 × 0.0333 + 0.05) = 0.15 pu, IR0 = abs(3 × 0.033 – (0.05)) = 0.05 pu, IR2 = 3 × 0.033 = 0.10 pu,
IR1 = 1.033 / 8 = 0.1292 pu, and Igr = 0.1292 pu
Despite very low fault current level, the differential current is above 100% of the restraining current.
Example 5: Internal low-current, high-load single-line-to-ground fault with no feed from the ground
Given the following inputs: IA = 1.10 pu ∠0°, IB = 1.0 pu ∠–120°, IC = 1.0 pu ∠120°, and IG = 0.0 pu ∠0°
The relay calculates the following values:
I_0 = 0.033 pu ∠0°, I_2 = 0.033 pu ∠0°, and I_1 = 1.033 pu ∠0°
Igd = abs(3 × 0.0333 + 0.0) = 0.10 pu, IR0 = abs(3 × 0.033 – (0.0)) = 0.10 pu, IR2 = 3 × 0.033 = 0.10 pu,
IR1 = 1.033 / 8 = 0.1292 pu, and Igr = 0.1292 pu
Despite very low fault current level the differential current is above 75% of the restraining current.
Example 6: Internal high-current single-line-to-ground fault with no feed from the ground
Given the following inputs: IA = 10 pu ∠0°, IB = 0 pu, IC = 0 pu, and IG = 0 pu
The relay calculates the following values:
I_0 = 3.3 pu ∠0°, I_2 = 3.3 pu ∠0°, and I_1 = 3.3 pu ∠0°
Igd = abs(3 × 3.3 + 0.0) = 10 pu, IR0 = abs(3 × 3.3 – (0.0)) = 10 pu, IR2 = 3 × 3.3 = 10 pu, IR1 = 3 × (3.33 – 3.33) = 0 pu, and
Igr = 10 pu
The differential current is 100% of the restraining current.
5.7.12 Negative sequence current
5.7.12.1 Menu
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEGATIVE SEQUENCE CURRENT
The L90 provides two negative-sequence time overcurrent elements, two negative-sequence instantaneous overcurrent
elements, and two negative-sequence directional overcurrent elements. For information on the negative sequence time
overcurrent curves, see the Inverse TOC Curve Characteristics section earlier.
5.7.12.2 Negative sequence time overcurrent (ANSI 51Q, IEC PTOC)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEGATIVE SEQUENCE CURRENT  NEG SEQ TOC1(2)
 NEGATIVE SEQUENCE
 CURRENT

 NEG SEQ TOC1

See below

 NEG SEQ TOC2


 NEG SEQ IOC1

See page 5-287

 NEG SEQ IOC2


 NEG SEQ DIR OC1

See page 5-288

 NEG SEQ DIR OC2

 NEG SEQ TOC1


NEG SEQ TOC1
FUNCTION: Disabled
Range: Disabled, Enabled

NEG SEQ TOC1 SIGNAL
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4

GE L90 Specifications

General

Brand	GE
Model	L90
Category	Relays
Language	English