2.0 Hacking in energy meters - Vulnerability and Solutions
Due to the increasing cost of electricity, energy theft is becoming a major concern for government agencies (Public Utility Boards) across the globe, and especially in populous countries like India and China.
A large portion of these revenue losses can be recovered by installing electronic energy meters because they can detect tampering conditions and assure proper billing, unlike electromechanical meters.
This section describes several tampering techniques used by thieves along with solutions for avoiding tampering.
2.1 Partial Earth Fault Condition
An earth fault means some of the load has been connected to another ground potential and not the neutral wire.
Figure 2 shows normal Phase and Neutral wire connections to the meter. Note that current going through the Phase wire is the same as coming out of the neutral wire (IP = IN).
Figure 2: Normal Phase Neutral Connection for Single Phase Meter
Figure 3 shows a Partial Earth Fault Condition where one of the loads is connected to the ground and thus part of the return current I2 does not go through the meter. Thus the current in the neutral wire IN, is less than that in the Phase or live wire (IP).
Figure 3: Partial Earth Fault Condition
To detect this condition, firmware monitors the currents on both energy wires - Phase and Neutral, and compares them. If they differ significantly, the firmware uses the larger of the two currents to determine the amount of energy to be billed and signals a "fault" condition.
2.2 Reverse Current
Reverse Current occurs when the phase and neutral are wired to the wrong inputs, causing current to flow in the direction opposite to normal. Figure 4 shows the same where the Neutral Wire connection is swapped thus causing current IN to flow in the reverse direction.
Figure 4: Reverse Current Condition
Due to the reverse current flow through Neutral, metering firmware will show wrong signs in active power readings. The firmware activates the reversed current indicator when any of the two currents has a sign opposite the one expected. To overcome this, metering firmware always uses the absolute value of active power for driving the energy pulse, thus reverse current has no effect on energy calculation or accurate billing.