IEEE C37.92-2005

This standard defines the interface between voltage or current transducer systems or sensing systems with analog electronic outputs, and suitably designed protective relays or other substation measuring equipment. These transducer systems reproduce the power system waveforms as scaled values. This standard also defines requirements for optional intermediate summing or ratio-adjusting amplifiers required to add or subtract the outputs of more than one sensing system for measurement by a single relay or measuring device.
The standardized measurement signal between the transducer system and the relay systems is characterized as an analog electrical signal of ±11.3 V peak, at a maximum power of 3.2 mW. A prime example of a sensing system with analog electronic output is an optical voltage or current sensing system with an optical-to-electronic interface. Figure 1 shows the typical configuration of system elements for an optical current sensing system in a high-voltage station. In this case the optical sensing systems are located on the bus at high potential. In other cases the sensing systems may be embedded inside power apparatus or insulators. The optical signal is transmitted through fiber-optic cables to the ground level before being converted to electrical signals scaled and formatted for use by protective relays and other intelligent electronic devices (IEDs). The optical-to-electrical conversion module is usually located in the control house, but may also be located near IEDs in the switchyard. This standard specifies the electrical signals between the optical-to-electrical conversion module and the relays or other IEDs using these signals. The interaction between the optical sensing system and the conversion module is a proprietary scheme of a particular manufacturer’s sensing design, not subject to standardization. It is the output of the conversion module, and therefore, the input of relays and other measuring functions, that is to be standardized here for interoperability. The marked section of Figure 1 shows the location of the interface defined in this standard.
New IEEE Standard – Inactive-Reserved. Electronic devices that develop or utilize analog signals are not presently covered by standards. This Standard provides interface connectivity of modern power-system signal transducers based on electronics, such as magneto-optic current transducers, and electronic relays. The existing standardized levels from familiar magnetic current and voltage transformers are not readily generated by new types of electronic signal transducers.