
2
1.0 Introduction
The Model B-291 Secondary Injection Test Set
is a single-phase test set specifically designed
for testing the operation of the Utility Relay
Co., AC-PRO microcontroller based trip units.
The test set will test either the standard 1-Amp
or the special 1/2-Amp AC-PRO.
The test set can test pick-up and time delays of
the various protection functions by driving
current into the AC-PRO on the secondary side
of the current transformer circuit.
The test set will test the AC-PRO trip system
with the exception of the current transformers
and associated wiring harness. Secondary
injection testing is not a substitute for
primary injection testing that should be
performed for any circuit breaker retrofit.
2.0 Overview
The basic function of the test set is to deliver an
accurate level of AC current directly to the
AC-PRO trip unit under test and to measure the
pick-up values and times required for the AC-
PRO to trip. The technician running the test
will operate the Start, Stop, Clear and Current
Preset momentary push buttons, adjust the Amp
Coarse and Amp Fine potentiometers (pots),
and adjust the Phase and Frequency Selector
switches. The two displays are used to indicate
elapsed time in seconds and test current in
amps.
Reference the AC-PRO users manual for the
AC-PRO operating instructions.
3.0 B-291 Test Set Controls
3.1 Power
Power to the test set is controlled with the
manual “On-Off” switch. An AC cord is
supplied with the test set. The recommended
AC power source is 120V AC at either 50 or 60
Hz. The “120 VAC” receptacle also contains
the 5 Amp, 250V, 5X20mm main power fuse.
3.2 Time Display
The B-291 test set will measure the time
elapsed while current is being delivered to the
AC-PRO, and display the time on the “Time
(seconds)” LCD display. The time will stop
accumulating when the AC-PRO trips or when
the Stop push button is pushed. The LCD time
display will display seconds with 1/100 of a
second resolution. The timer display is cleared
when the Clear push button is pushed.
3.3 Timer Clear Push Button
The “Clear” push button clears the time
display.
3.4 Start Push Button and LED
The “Start” push button starts the test current
flow to the AC-PRO and simultaneously starts
the timer. The green LED located above the
Start push button indicates test current flow.