GE Industrial Solutions Entellisys 4.0 System User Manual - Manual (Page 68)

Single point functions 68
5
Inverse time function: If the inverse time curve is selected, the system trips the appropriate
circuit breaker or activates an alarm according to the equation:
The parameters in this equation are defined as:
T = operating time
D = delay setting
V = input voltage
V
pickup
= pickup voltage = (set point) × (nominal voltage)
Trip time accuracy: Trip time accuracy depends on the value of V/V
pickup
. The closer that ratio is
to 1, the larger the trip time error is for a given pickup error. For V/V
pickup
= 0.8, the trip time
accuracy is ± 10%. For V/V
pickup
= 0.5, the trip time accuracy is ± 4%.
Blocking voltage option: A 'blocking voltage' user-defined input option is provided. The
Undervoltage Relay function is not performed if the blocking voltage option is enabled and the
voltages on all three phases are less than the blocking voltage setting. If the Undervoltage Relay
goes into pickup, and the voltages subsequently drop below the blocking voltage, the relay goes
out of pickup and the delay is reset.
Accuracy: Pickup accuracy is ± 2%.
5.2.1.1 Setup
To set the Trip and Alarm settings for the Undervoltage Relay function
1. On the Main Menu, click User Settings, and then select Relay Protection.
2. On the Relay Protection screen, choose the circuit breaker number from the drop-down
menu and click Undervoltage.
The remainder of this section discusses the relay parameters that can be set in the
Undervoltage section of the Relay Protection screen as shown in Figure 5-4.
5.2.1.2 Trip settings
Relay Enabled: Select Enabled to enable the relay.
Curve Type: Select either Constant time curve or Inverse time curve from the Curve Type
drop-down menu.
Pickup: Adjust the undervoltage pickup from 10% to 95% in increments of 1% from the Pickup
Setting drop-down menu.
Delay: Adjust the undervoltage delay from 0.5 to 600 seconds in increments of 0.5 seconds from
the Time Delay drop-down menu.
( )
pickup
V V - 1
D
T
=