6.6
SEL-2414 Transformer Monitor Instruction Manual Date Code 20130214
Settings
Device Settings (SET Command)
Device setting PTR is the potential transformer ratio from the primary system to
the voltage terminals of the device. See voltage input details in Figure 2.17.
Analog Inputs
For an SEL-2414 configuration without voltage or current cards, the device sam-
ples all analog inputs at a fixed value of 4 ms regardless of the frequency of the
power system. When the SEL-2414 configuration includes either voltage or cur-
rent cards (or both), the device tracks the frequency (using positive-sequence
quantities), and samples the analog inputs four times per power system cycle; see
Sampling and Processing Specifications on page 1.10 for more information. For
the eight analog inputs, set the following parameters for each input:
➤ Analog type
➤ High and low input levels
➤ Engineering units
Because of the flexibility to install different cards in the rear-panel slots of the
device, the setting prompt adapts to the x and y variables shown in Figure 6.2.
Var iable x displays the slot position (3 through 6), and variable y displays the
transducer (analog) input number (1 through 8).
Analog Input Calibration Process
In the analog input circuit, the dominant error is signal offset. To minimize the
signal offset, we adjust each of the device analog input channels by a compensa-
tion factor. These compensation factors correct the signal offset errors to within
±1 uA or ±1 mV.
Signal offset compensation factor calculation procedure:
1. Turn the SEL-2414 on and allow it to warm up for a few minutes.
2. Set the analog inputs for each analog channel to the desired range
(e.g., ±1 mA), using the AIxxxTYP, AIxxxL, and AIxxxH
settings.
3. Short each analog input in turn at the device terminals using short,
low resistance leads with solid connections.
4. Issue the command MET AI 10 to obtain ten measurements for
each channel.
5. Record these ten measurements, then calculate the average of the
ten measurements by adding the ten values algebraically, and
dividing the sum by ten. This is the average offset error (e.g.,
–0.014 mA).
6. Negate this value (i.e., flip the sign) and add the result to each of
the AIxxxL and AIxxxH quantities. For this example, the new
AIxxxL and AIxxxH values are –0.986 mA and 1.014 mA.
Figure 6.2 Analog Input Names
Inputs Number (1 through 8)
Slot Position (3 through 6)
Analog Input
AIx0y
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