GE 845

CHAPTER 1: INTRODUCTION SPECIFICATIONS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 1–23
DEMAND
Measured Values:................................................Phase A/B/C present and maximum current
Measurement Type:...........................................Thermal Exponential, 90% response time (programmed): 5,
10, 15, 20, 30 minutes
Block Interval / Rolling Demand, time interval (programmed):
5, 10, 15, 20, 30 minutes
Current Pickup Level:.........................................10 to 10000 in steps of 1 A
Dropout Level: ......................................................96-98% of Pickup level
Level Accuracy:....................................................± 2%
NOTE
NOTE:
Factory tested at 25°C
Inputs
AC CURRENTS
CT Rated Primary:...............................................1 to 12000 A
CT Rated Secondary:.........................................1 A or 5 A based on relay ordering
Burden: ....................................................................< 0.2 VA at rated secondary
Short Term CT Withstand:...............................1 second at 100 x rated current
2 seconds at 40 x rated current
continuous at 3 x rated current
AC VOLTAGE
VT Range:................................................................10 to 260 V
Nominal Frequency:..........................................20 to 65 Hz
Burden: ....................................................................<0.25 VA at 120 V
Conversion Range: .............................................1 to 275 V
Voltage Withstand:.............................................continuous at 260 V to neutral
1 min/hr at 420 V to neutral
ANALOG INPUTS
Current Input (mA DC):......................................0 to 1mA, 0 to 5mA, 0 to 10mA, 0 to 20mA, 4 to 20mA
(configurable)
Input Impedance:................................................375  ± 10%
Conversion range: ..............................................0 to +21 mA DC
Accuracy:................................................................± 1% of full scale,
Type: .........................................................................Passive
Analog Input Supply:.........................................+24 V DC at 100 mA max.
Sampling Interval: ..............................................Typically 500 ms
FREQUENCY
Nominal frequency setting: ...........................50 Hz, 60 Hz
Sampling frequency:.........................................64 samples per power cycle
128 samples per power cycle (available for transient
recorder
Tracking frequency range:.............................3 to 72 Hz