System Operator Certification Curriculum Excerpts

Northwest Lineman College

SYSTEM OPERATOR CERTIFICATION PROGRAM

CURRICULUM SAMPLE EXCERPTS

SUBSTATION COMMUNICATION SYSTEMS Northwest Lineman College

Modems are commonly used to modulate an analog carrier signal.

SCADA systems are used to control fans and monitor transformer temperatures.

SCADA systems receive current inputs from current transformers.

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This 15 kV circuit breaker is monitored and controlled via SCADA.

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IEEE 1379-2000 standard recommends a set of best practices for implementing modern SCADA Master-RTU/IED communication links. The standard references DNP3 as the communications protocol to be considered for SCADA systems.

DNP3 (Distributed Network Protocol) is a set of communications protocols used between components in process automation systems. Its main use is in utilities such as electric and water companies. It was developed for communications between various types of data acquisition and control equipment. It plays a crucial role in SCADA systems, where it is used by SCADA Master Stations, Remote Terminal Units (RTUs), and Intelligent Electronic Devices (IEDs). It is primarily used for communications between a master station and RTUs or IEDs. ICCP, the Inter-Control Centre Protocol, is used for inter-master station communications.

The DNP3 protocol supports time synchronization with an RTU. The DNP protocol has time stamped variants of all point data objects so that even with infrequent RTU polling, it is still possible to receive enough data to reconstruct a sequence of events of what happened in between the polls. A Remote Terminal Unit for the DNP3 protocol can be a very small, simple embedded device, or it can be a very large, complex rack filled with equipment.

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IEEE STANDARD 1379-2000 AND DNP3

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CHAPTER FOUR | SUBSTATION COMMUNICATION SYSTEMS

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While this protocol is robust, efficient, compatible, and secure, it is getting more and more complex and subtle as it ages. While this is partly due to more demanding industrial applications, it is also a reflection that SCADA concepts are not as simple as they might first seem. The goal of compatibility is more important than ever, as advancement in use of SCADA for delivering smart grid concepts becomes a reality.

SCADA Master Station/Control Center

Comm. Links

Remote Substation

1200 bps + (down to 300 bps in actual installations)

Intelligent Electronic Devices

Radio Microwave Spread-spectrum

HMI/SCADA Master External Control Points

Twisted-pair Fiber-optics Dial-up Leased Line

Meter

Remote Terminal Unit (RTU)

Accumulator

Northwest Lineman College

Actuator

Programmable Logic Controller (PLC)

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© 2016 Northwest Lineman College Published February 2016