Basler BE1-11g Instruction Manual page 60

48
140%
135%
130%
125%
120%
115%
110%
105%
100%
1.0
Assuming a Vnom of 69.3 Vpn, 1 pu volts/hertz = (69.3 * √3) / 60 = 2.00. Using IEEE Std C37.102-2006 -
IEEE Guide for AC Generator Protection as a guide for setting overexcitation protection, the following
example demonstrates how to set the BE1-11g to provide a composite V/Hz characteristic for protection
of a generator and a step-up transformer:
• Alarm = 105% @ 1 second time delay; V/Hz = 2 * 1.05 = 2.10
•
Inverse time pickup = 105%; Time Dial = 1.9; Inverse Trip Curve = (M-1)^2; V/Hz = 2 * 1.05 = 2.10
• Definite Time #1 = 118% @ 6 seconds time delay; V/Hz = 1.18 * 2.0 = 2.36
The reset rate is determined by the Reset Dial setting. A setting of zero (0) gives an instantaneous reset.
Using the inverse squared characteristic, assume a trip time dial setting 2.0 and a pickup multiple of 1.2.
The total time to trip will be 50 seconds. If this exists for 30 seconds before being corrected (60% elapsed
time), what would the total reset time be for a reset dial setting of 5? Based on the reset equation
(Equation 5), the calculation will be:
T
R
If the overexcitation condition returns prior to total reset (i.e., less than 300 seconds), timing resumes from
that point at the inverse square rate. For example, if this condition recurs after 150 seconds or 50% of the
total reset time, then trip time from the second event will start at 30% instead of 0%, therefore tripping in
70% of the original trip time or 35 seconds. Figure 40 illustrates the inverse time delay and reset time.
Overexcitation (24) Protection
Volt/Hz Characteristic
Definite
118%, 6s
10.0
Figure 39. Time Shown on Horizontal Axis
E
= ∗ ∗
T
D 100
R
FST
Equation 5. Time to Reset
Transformer Limit
Inverse
105%, TD=1.9
100.0
Time in Seconds
30
= ∗ ∗ =
T 5 0 . 100 300
R
50
9424200994 Rev U
Generator Limit
1000.0
D2871-43
02-12-04
seconds
BE1-11g