b) CT/VT MODULE CONFIGURATIONS
CT and VT input channels are contained in CT/VT modules in UR products. The type of input channel can be phase/neu-
tral/other voltage, phase/ground current, or sensitive ground current. The CT/VT modules calculate total waveform RMS
levels, fundamental frequency phasors, symmetrical components and harmonics for voltage or current, as allowed by the
hardware in each channel. These modules may calculate other parameters as directed by the CPU module.
A CT/VT module can contain up to eight input channels numbered 1 through 8. The numbering of channels in a CT/VT
module corresponds to the module terminal numbering of 1 through 8 and is arranged as follows; channels 1, 2, 3 and 4
are always provided as a group, hereafter called a "bank," and all four are either current or voltage, as are channels 5, 6, 7
and 8. Channels 1, 2, 3 and 5, 6, 7 are arranged as phase A, B and C respectively. Channels 4 and 8 are either another
current or voltage.
Banks are ordered sequentially from the block of lower-numbered channels to the block of higher-numbered channels, and
from the CT/VT module with the lowest slot position letter to the module with the highest slot position letter, as follows:
INCREASING SLOT POSITION LETTER -->
CT/VT MODULE 1
< bank 1 >
< bank 2 >
The UR platform allows for a maximum of three sets of three-phase voltages and six sets of three-phase currents. The
result of these restrictions leads to the maximum number of CT/VT modules in a chassis to three. The maximum number of
Sources is six. A summary of CT/VT module configurations is shown below.
CT Bank (3 phase channels, 1 ground channel)
VT Bank (3 phase channels, 1 auxiliary channel)
c) CT/VT INPUT CHANNEL CONFIGURATION SETTINGS
Upon startup of the relay, configuration settings for every bank of current or voltage input channels in the relay are automat-
ically generated, as determined from the order code. Within each bank, a channel identification label is automatically
assigned to each bank of channels in a given product. The 'bank' naming convention is based on the physical location of
the channels, required by the user to know how to connect the relay to external circuits. Bank identification consists of the
letter designation of the slot in which the CT/VT module is mounted as the first character, followed by numbers indicating
the channel, either 1 or 5.
For three-phase channel sets, the number of the lowest numbered channel identifies the set. For example, F1 represents
the three-phase channel set of F1/F2/F3, where F is the slot letter and 1 is the first channel of the set of three channels.
Upon startup, the CPU configures the settings required to characterize the current and voltage inputs, and will display them
in the appropriate section in the sequence of the banks (as described above) as shown below for a maximum configuration:
F1, F5, L1, L5, S1, S5
The above section explains how the input channels are identified and configured to the specific application instrument
transformers and the connections of these transformers. The specific parameters to be used by each measuring element
and comparator, and some actual values are controlled by selecting a specific Source. The Source is a group of current
and voltage input channels selected by the user to facilitate this selection. With this mechanism, a user does not have to
make multiple selections of voltage and current for those elements that need both parameters, such as a distance element
or a watt calculation. It also gathers associated parameters for display purposes.
The basic idea of arranging a Source is to select a point on the power system where information is of interest. An applica-
tion example of the grouping of parameters in a Source is a transformer winding, on which a three phase voltage is mea-
sured, and the sum of the currents from CTs on each of two breakers is required to measure the winding current flow.
CT/VT MODULE 2
CT/VT MODULE 3
< bank 3 >
< bank 5 >
< bank 4 >
< bank 6 >
L90 Line Differential Relay
GE Power Management