Electrical Energy meters are sealed to detect possible manipulations. They are not preventing tamper, but at least you know that someone has broken the seal and eventually manipulated the meter.
The utility field workers check the meter installations regular. If a broken seal is found, the reason will be investigated. Special field test equipment helps to verify the complete meter installation.
When the power company is using numbered seals, the existing installation is verified vs. the initial seal numbers. This is an additional measure to detect tamper.
If there is no specific utility request for numbered seals, the produced meters leave the factory with un-numbered seals. This seals are assuring that there was no manipulation during the transport. It’s highly recommended that the utility replaces this seals with their own sealing scheme.
Sealing of electrical energy meter installations
This is a general selection, not all meters have all sealing positions.
- Terminal cover
The terminal cover has one or two seals to make the customer more sensitive that unauthorised opening of energy meters is forbidden. Electronic meters are also detecting when the terminal cover has been opened. Depending on the utility settings the internal relay will trip. It can only be reset by the power supply company.
If an AMI system is installed, the utility operator receives an alarm. Date and time of opening are internally recorded. The detection also can work when the meter is not energized.
- Main cover
The main meter cover has typically two seals. Meters with a ultrasonic welding don’t need seals as the main cover will be destroyed during the opening event. In any case an un-authorized opening will be detected and processed in the same way like the terminal cover opening.
- Maximum demand reset button
- Battery slot
- Slot for exchangeable communication module
- Optical communication port
- Enclosure for the meter
- Terminals for the instrument transformers (CT-meters)
- CT-meter switch board
The twist lock seal doesn’t require an additional tool for fixing. The seal number can be wittten by laser on the front plate.
High end digital sealing method
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Thank you for reading.
Editor's note: This article was originally published in December 2019 and has been updated for comprehensiveness.