4.212
SEL-700G Relay
Instruction Manual
Date Code 20170814
Protection and Logic Functions
Global Settings (SET G Command)
Analog Inputs
The SEL-700G tracks the power system frequency and samples the analog
inputs four times per power system cycle. For analog inputs, set the following
parameters for each input:
➤
Analog type
➤
High and low input levels
➤
Engineering units
You can install different cards in the rear-panel slots of the SEL-700G relays.
The relay setting prompt adapts to the x and y variables shown in
Figure 4.141. Variable x displays the slot position (
3
through
5
), and variable y
displays the transducer (analog) input number (1 through 4).
Figure 4.141
Analog Input Card Adaptive Name
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
compensation factor. These compensation factors correct the signal offset
errors to within ±1 µA or ±1 mV.
The signal offset compensation factor calculation procedure is as follows:
1. Turn the SEL-700G on and allow it to warm up for a few
minutes.
2. Set the analog inputs for each analog channel to the necessary
range, by using the AIxxxTYP, AIxxxL, AIxxxH, AIxxxEL, and
AIxxxEH settings (for example, ±1 mA).
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 10 measurements for
each channel.
5. Record these 10 measurements, then calculate the average of
the 10 measurements by adding the 10 values algebraically and
dividing the sum by 10. This is the average offset error in
engineering units at zero input (for example, –0.014 mA).
6. Negate this value (flip the sign) and add the result to each of the
AIxxxEL and AIxxxEH quantities. For this example, the new
AIxxxEL and AIxxxEH values are –0.986 mA and 1.014 mA.
Analog Input Setting Example
Assume that we installed an analog card in Slot
3
. On Input 1 of this analog
card, we connect a 4–20 mA transducer driven from a device that measures
temperature on a transformer load tap changer mechanism. For this
temperature transducer, 4 mA corresponds to –50°C, and 20 mA corresponds
to 150°C. You have already installed the correct hardware jumper (see
Figure 2.3 for more information) for Input 1 to operate as a current input. At
power up, allow approximately five seconds for the SEL-700G to boot up,
perform self-diagnostics, and detect installed cards. Table 4.67 summarizes
the steps and describes the settings we carry out in this example.
Inputs Number (1 through 4)
Slot Position (3 through 5)
Analog Input
AIx0y
Summary of Contents for SEL-700G Series
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