ADVANCED OPERATION - Section 5
MTS-3000 SERIES OPERATION AND REFERENCE MANUAL 5-9
CU M004 01A
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The menu-driven Frequency 2 option normally only will be required where it’s desired to have two
internally-generated frequencies simultaneously. This would be the case where the mains frequency is
somewhat unstable as, for example, when a portable generator is supplying the mains. In this event, first
program Frequency 1, as above, and assign it to one or more outputs, as required. The remaining outputs
will be at line frequency, but will change to Frequency 2 when programmed by the Frequency 2 menu
option.
5.2.7 Breaker Times
(Bkr Times)
This feature facilitates an accurate simulation of power system performance by delaying the tripping or
reclosing of AC outputs by a specified time to account for the operate time of a circuit breaker. In the real
world, an overcurrent situation, for example, doesn’t clear immediately upon operation of a relay contact
responding to the overcurrent, but when the main contacts of the circuit breaker controlled by that contact
open. This feature can be particularly useful in verifying the operation of breaker failure protection systems.
5.2.8 AC Current Range
(ACI Range)
There are two fixed ranges of compliance voltage available from the current output channels of the system.
By default, the system is configured for high current, low compliance voltage. Most current-operated
relays are specifically designed for low impedance burden. Subsequently, for the majority of applications,
including virtually all modern microprocessor-based relay testing, the default configuration of the system
is the best choice since it offers the highest possible current.
There are some applications, however, particularly electromechanical ground protection relays, which may
present significant burdens, as much as 25 ohms. These devices usually have lower current settings, but
their high burden can make it difficult to pass current through them. It would take a 20 V source to pass
just 1 A through a 20 ohm relay, for example.
The default current range of the MTS current sources supplies 25 A per channel at up to 15 V. Whenever
the product of the combined test lead impedance plus relay impedance, times the current output, exceeds
15 V, a "Output x Clip’ng" alarm subsequently will be generated and current distortion will increase. Note
that paralleling current outputs for this situation won’t resolve the problem since the total compliance
voltage of current channels operated in parallel doesn’t increase above that of a single channel.
To select the high compliance voltage range, enter the following key sequence: MENU | Settings | Current
range | 0-12A, High V. Note that the compliance voltage available will be doubled at the expense of
reducing, by 50%, the amount of current available. Maximum current will be 12 A at up to 30 V. It’s
particularly important to use securely fastened high quality large gage test leads if experiencing problems
in testing into high burden loads.
5.2.9 Reclose
This feature allows a variety of reclosure scenarios to be programmed.
Shots determines the number of times a reclosure will be initiated before locking out from further operation
when using the "internal" reclose option.