Utility revenue loss due to fraud, including meter tampering, is estimated at 2% in the USA and even higher for electricity providers worldwide. Because of the economic incentives to reduce an electricity bill, many users resort to illegal meter tampering. Traditionally, this involved simply damaging or hindering the rotation of an electromechanical watthour meter.

Advances in technology have made it easier for utilities to read electricity meters from a remote location. But this same technology has provided the means for unauthorised persons to tamper with meters and reduce the billed energy usage or demand without being detected. Frequently, the meters for large customers are read by remote means, and remote communications are the most susceptible to interception.

Until now, many meter manufacturers relied on password security to prevent unauthorised access to a meter read by a telephone circuit. Unfortunately, the same technology that makes telephone meter reading possible makes it relatively easy for those calls to be intercepted.


Take, for example, a hypothetical case of a large industrial electricity user with an electronic meter read by a telephone link to the local electricity utility. To prevent meter tampering, the utility encloses the meter and modem in a locked cabinet. In order to read the meter, the utility initiates a call, normally at a set time of the month. The utility reads the meter electronically and resets the demand. For security, the reading device must send a password to the meter before it can retrieve the data and reset the demand.

An unauthorised person who wants to change meter parameters, or at least reset the demand recorder, needs the password. The problem, or opportunity, is that while the meter and modem are secure inside the locked cabinet, the phone line is not secure. In many cases, the utility uses a customer’s phone line, or even a cell phone, to read the meter. Neither of these two methods prevents a moderately knowledgeable energy thief from intercepting the meter reading data exchange and obtaining the password. An unauthorised person with the password can reset, reprogram, or otherwise compromise the meter. The utility then loses significant revenue, with no way of identifying the person responsible, even if the theft itself is detected.

To prevent theft, the utility must have either a completely secure communications link (almost impossible to obtain if any type of over-the-air or public communications channel is used) or a means of encrypting communication to the meter so that no unauthorised person can intercept the call.


The SEL-3021 Serial Encrypting Transceiver from Schweitzer Engineering Laboratories, Inc. introduces a simple means to provide virtually unbreakable encryption for communications from a central location to the serial port of the meter. Communications security is established by connecting one SEL-3021 at the meter reading headquarters and another one between the modem and each meter to be read by telephone. Using 128-bit encryption keys, the SEL-3021 sends a message that cannot be deciphered by anyone without the key, and that key is selected and programmed by the utility.

Advances in communications have made it easier for energy thieves to intercept and tamper with meter communications. Fortunately other advances, such as the SEL-3021, have made it possible to prevent data interception and energy theft. Visit www.selinc.com/mi1 to learn more about how you can prevent serial communications from being intercepted by intruders.