The Help Key; Numerical Setpoints - GE 750 Instruction Manual

750/760
Feeder Management Relay

The HELP Key

Numerical Setpoints

1–6
access terminals (C10 and C11) on the back of the relay case. Attempts to enter a
new setpoint without this electrical connection will result in an error message.
The jumper does not restrict setpoint access via serial communications. The relay
has a programmable passcode setpoint, which may be used to disallow setpoint
changes from both the front panel and the serial communications ports. This
passcode consists of up to eight (8) alphanumeric characters.
The factory default passcode is "0". When this specific value is programmed into the
relay it has the effect of removing all setpoint modification restrictions. Therefore,
only the setpoint access jumper can be used to restrict setpoint access via the front
panel and there are no restrictions via the communications ports.
When the passcode is programmed to any other value, setpoint access is restricted
for the front panel and all communications ports. Access is not permitted until the
passcode is entered via the keypad or is programmed into a specific register (via
communications). Note that enabling setpoint access on one interface does not
automatically enable access for any of the other interfaces (i.e., the passcode must
be explicitly set in the relay via the interface from which access is desired).
A front panel command can disable setpoint access once all modifications are
complete. For the communications ports, writing an invalid passcode into the
register previously used to enable setpoint access disables access. In addition,
setpoint access is automatically disabled on an interface if no activity is detected for
thirty minutes.
The EnerVista 750/760 setup software incorporates a facility for programming the
relay's passcode as well as enabling and disabling setpoint access. For example,
when an attempt is made to modify a setpoint but access is restricted, the software
will prompt the user to enter the passcode and send it to the relay before the
setpoint is actually written to the relay. If a SCADA system is used for relay
programming, it is the programmer's responsibility to incorporate appropriate
security for the application.
Pressing the HELP key displays context-sensitive information about setpoints such as
the range of values and the method of changing the setpoint. Help messages will
automatically scroll through all messages currently appropriate.
Each numerical setpoint has its own minimum, maximum, and step value. These
parameters define the acceptable setpoint value range. Two methods of editing and
storing a numerical setpoint value are available.
The first method uses the 750/760 numeric keypad in the same way as any
electronic calculator. A number is entered one digit at a time with the 0 to 9 and
decimal keys. The left-most digit is entered first and the right-most digit is entered
last. Pressing ESCAPE before the ENTER key returns the original value to the display.
The second method uses the VALUE
step value, up to a maximum allowed and then wraps around to the minimum value.
Likewise, the VALUE key decrements the displayed value by the step value, down to
a minimum value and then wraps around to the maximum value.
For example:
1. Select the
S2 SYSTEM SETUP
setpoint message.
NOMINAL VT SECONDARY
VOLTAGE: 120.0 V
2. Press the 6, 3, decimal, and 9 keys. The display message will change as shown.
NOMINAL VT SECONDARY
VOLTAGE: 63.9 V
3. Until the ENTER key is pressed, editing changes are not registered by the relay.
Therefore, press the ENTER key to store the new value in memory. This flash
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key to increment the displayed value by the
BUS VT SENSING NOMINAL VT SECONDARY VOLTAGE
Changing Setpoints
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