Landis & Gyr Cashpower Gemini HMI User Manual - 7.6
General Meter Operation Released
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Cashpower Gemini HMI
– User Guide
© Landis+Gyr (Pty) Ltd
7.6
Reverse Power Detection and Metering
The metering circuitry can detect and measure reverse power. A filter ensures that short periods of
reverse power are ignored e.g. as a result of a motor running down and only significant reverse power
detected. A significant reverse power condition will be flagged when there has been a continuous
reverse power measurement equivalent to 50Wh.
Under reverse power conditions, metering will continue as normal i.e. credit will continue to be
decremented.
A setting in the option register (refer to section 13.18) determines whether the meter should ignore a
reverse power condition, or act on it by entering into the tampered state.
If the tamper on significant reverse power option is set, the meter will enter into the tampered state
and open the load switch, thus disconnecting the supply of electricity to the customer.
If the tamper on significant reverse power option is not set, the meter will continue to meter energy
usage in the normal way.
Once significant reverse energy has been detected and flagged, it can only be reset with a valid
tamper reset token.
7.7
Automatic/Manual Load Reconnection
In some instances, local safety regulations require that the meter not automatically re-close the load
switch after, for example, a power limit trip. Under these conditions, the load switch will remain in the
open state until such time as any key on the keypad is pressed.
Using the example of a power limit trip (refer to section 7.5), the load switch will open and remain open
for a period of 30 seconds. At the end of this 30-second period, the display will return to normal but,
instead of the load switch closing, the load switch status icon on the LCD will start to flash, toggling
between an open and closed state. This is the indication that the load switch may now be manually
closed, by pressing any key on the keypad.
In the event of the load switch opening due to expiry of credit, it will only be able to close again on
entry of a valid credit token. The manual action of entering a credit token via the keypad, results in the
load switch closing when the last digit of the token is entered and accepted by the meter.
Automatic/manual load reconnection is a configurable option, set at the time of manufacture (refer to
section 13.18). It may also be changed at any stage with a suitable engineering token.
7.8
Disconnect on Power Failure
This option, configurable at the time of manufacture (refer to section 13.18), forces
the meter‟s load
switch to open whenever there is a power failure. This can minimise attempts at fraud by, for
example, cutting the neutral supply wire to the meter.
7.9
Optical Port
The Gemini HMI meter is provided with an optical interrogation port that allows two way
communications with the meter.
The communications protocol complies with IEC 62056-21 mode C.
7.10 Credit Reader Interface
This port is available via a removable plug at the rear of the meter and should only be accessed when
the meter is disconnected from power. It allows for meter data such as remaining credit to be
extracted in the event of an electronics failure.
From a safety point of view, the meter must not be powered when accessing this
port
– the Credit Reader provides the necessary low-voltage supply to power the
logic circuitry.