Setpoint Group; Differential - GE 745 TRANSFORMER MANAGEMENT RELAY Instruction Manual

5.6 S4 ELEMENTS
Each protection and monitoring element setpoint (programmed in S4 ELEMENTS) has four copies, and these set-
tings are organized in four setpoint groups. Only one group of settings are active in the protection scheme at a
time. The active group can be selected using the ACTIVE SETPOINT GROUP setpoint or using a logic input. The
setpoints in any group can be viewed or edited using the EDIT SETPOINT GROUP setpoint.
S SETPOINT GROUP
S [ENTER] for more
ACTIVE SETPOINT
GROUP: Group 1
EDIT SETPOINT
GROUP: Active Group
GROUP 2 ACTIVATE
SIGNAL: Disabled
5
This section contains the settings to configure the percent differential element, including all associated har-
monic inhibit features. The 745 provides three independent harmonic inhibit features: HARMONIC INHIBIT, which
implements an inhibit scheme based on 2
INHIBIT, which allows changing the characteristics of the inhibit scheme during energization to improve reliability;
and 5TH HARMONIC INHIBIT, which implements an inhibit scheme based on 5
the percent differential during intentional overexcitation of the system.
S DIFFERENTIAL
S [ENTER] for more
a) PERCENT DIFFERENTIAL
This section contains the settings to configure the percent differential element. The main purpose of the per-
cent-slope characteristic of the differential element is to prevent maloperation because of unbalances between
CTs during external faults. These unbalances arise as a result of the following factors:
• CT ratio mismatch (not a factor, since the 745 automatically corrects for this mismatch)
• Onload tap changers which result in dynamically changing CT mismatch
• CT accuracy errors
• CT saturation
5-46
This message indicates the start of the SETPOINT GROUP section. To continue
with these setpoints press
section.
Range: Group 1 / Group 2 / Group 3 / Group 4
Select the number of the SETPOINT GROUP whose settings are to be active in
the protection scheme. This selection will be overridden if a higher number
setpoint group is activated using logic inputs.
Range: Group 1 / Group 2 / Group 3 / Group 4 / Active Group
Select the number of the SETPOINT GROUP whose settings are to be viewed
and/or edited via the front panel keypad or any of the communication ports.
Selecting Active Group selects the currently active setpoint group for editing.
Range: Disabled / Logc Inpt 1 (2-16)
Select any logic input which, when asserted, will (remotely) select SETPOINT
GROUP 2 (3-4) to be the active group. This selection will be overridden if a
higher number setpoint group is activated using the ACTIVE SETPOINT GROUP
setpoint or another logic input.
nd nd th
or 2 + 5 harmonic which is 'in-circuit' at all times; ENERGIZATION
This message indicates the start of the DIFFERENTIAL section. To continue
these setpoints, press
EN TE R
745 Transformer Management Relay

5.6.3 SETPOINT GROUP

, or press
E N TE R M E SSA G E

5.6.4 DIFFERENTIAL

th
harmonic only, allowing inhibiting
, or press to go to the next section.
M E SS AG E
GE Power Management
5 SETPOINTS
to go to the next