Manta MTS-3000 Series, Operation And Reference Manual, Page: 78 / 156

ADVANCED OPERATION - Section 5
5-6 MTS-3000 SERIES OPERATION AND REFERENCE MANUAL
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5.2.3 Harmonics
This submenu offers the ability to program any AC output channel with one of several forms of harmonic
distortion. This is a requirement for testing certain relay types, such as transformer current differential or
generator stator ground, which rely on the detection of specified harmonics to reliably protect against faults.
ACV1
Φ
A Harm refers to the A phase of the #1 AC Voltage module (it’s possible to have more than one
Voltage module in a stack). ACI1
Φ
C will subsequently refer to the C phase of the #1 Current module.
5.2.3.1 HARMONICS OPTIONS.
These include Harmonics OFF (the default state), Harm.[onics] Alone, and Fund[amental] + Harm.[onic].
The last option is the one most commonly used for verifying the second harmonic inrush restraint feature
of transformer current differential protection relays. The programmable settings available for this selection
are:
Harmonic # 2
nd
to 10
th
Harmonic amplitude 0 to 50% (*based on classical formula, see below)
Phase angle 0.0 to 359.9
°
(relative to fundamental)
* The traditional way to produce second harmonic content to test the harmonic restraint feature of
transformer differential current relays was to combine pure AC current (I
ac
) measured with an RMS
responding meter with ½ wave rectified DC current (I
dc
) measured with an average responding meter.
The resulting harmonic content can then be calculated from:
% 2
nd
Harmonic = ((0.424 I
dc
)/ (0.9I
ac
+ I
dc
)) x 100
5.2.4 Parallel Current
This option may be accessed when it’s desired to output more AC current than can be produced by a single
current channel. It’s possible to achieve this result manually by setting the phase angle on each paralleled
channel to the same figure, and setting the amplitudes the same. It’s more convenient and faster, however,
to use this option since it will automatically synchronize the phase angles, adjust all paralleled channel
amplitudes simultaneously with a single MODIFY input, and display the total paralleled current available
on the fourth line of each current module.
Before selecting this option, verify that the fault mode has been selected for Vector mode or
Φ
-N mode, as
indicated in the lower left corner of the main display. The
Φ
-
Φ
and 3
Φ
fault modes inherently are designed
to manipulate currents with three different phase angles. If the fault type is currently selected for
Φ
-
Φ
or
3
Φ
fault type, enter the following key sequence: MENU | Settings | Fault Type | Vector.
Because it’s possible to have more than one current module in a stack, provision has been made to allow
for up to three individual paralleled current groups, and any one current channel can be assigned to any of
the three possible groups. This assignment process is shown in the illustration on the next page.
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