The Role of Power System Operators

Power System Operator

The Role of Power System Operators 

The power system operators are mostly concerned with the reliability or security of the power grid. Operators control the actual flow of electric power from the power plant to the customers. They also work with neighboring control areas to manage the import and export of power. Matching the supply of power to the demand of consumers is one of the main focuses of these operators. 

Tasks and operations performed during normal conditions 

There are many tasks and operations performed during normal conditions. The following functions are the most fundamental operator role. 

Dispatch and Control -- They operate high voltage direct current converter equipment, tap changing transformers, phase shifting transformers, and circuit breakers as well as voltage control equipment. Dispatchers monitor equipment and record readings at a pilot board, which is a map of the transmission grid system showing the status of transmission circuits and connections with substations and industrial plants. There are many times when all you have to do is monitor the system. It is important that you be there, but the hours may seem long, especially when the system is running well and there is little maintenance activity being performed. 

Energy Demand Forecasting -- The most important task performed is the projection of the customer’s energy requirements on a near-term basis. This is normally a projection of hourly megawatts of power for the next 24 to 96 hours. This projection is based upon historical load patterns and weather projections. Depending on where located above the equator, your load patterns can very significantly between winter, summer, spring and fall due to time sunrise and sunset and temperature conditions. Other factors affecting load patterns include cloud cover, day of the week and holidays. 

Energy Demand

Market Authority -- Market and Interchange Transaction Operators’ focus is placed on the wholesale energy market. They also work with the rest of operations to mitigate problems in the event of a security violation.

European Electricity Spot Market

Monitor Load to Capacity Resources -- The next step is to enter the projected purchases and sales on an hourly total basis into the automatic generation control program. This automatic generation control program performs balancing between generation, customer load requirements and purchases and sales and provides its frequency bias obligation. 

Monitoring Frequency -- This automatic generation control program also maintains a constant frequency and accurate time. If a party's generation is unable to perform its balancing obligation, frequency will deviate from 60 hertz and create an inaccuracy in time. When a frequency deviation occurs, the automatic generation control program applies its frequency bias calculation to bring frequency back to normal. 

Energy Reconciliation -- Another task, energy accounting, is an after-the-fact reconciliation of scheduled transactions with other utilities and the actual deliveries including losses. During this reconciliation, differences between scheduled the actual deliveries are determined and accumulated inadvertent energy. In most cases, the inadvertent energy is corrected through a payback arrangement. 

Power Outage Coordination -- Another task, just as important, is the scheduling of equipment outages for maintenance and other reasons. This requires communication and coordination with the maintenance people requesting authorization to work on electrical equipment. In order to perform work on an electrical system, a permit or clearance is required. In order to provide a clearance or permit, studies must be done to determine the consequence of taking the equipment out of services during the requested time frame. 

Technician Repairing a Transmission Line during Power Outage

Many times this requires coordination with the regional reliability authority. These studies are performed on a first contingency basis. In other words, the system must remain stable and secure during the outage period with the worst contingency occurring. This analysis is done with modern computerized models of the electric transmission systems. The outage scheduling task is performed by the group responsible for transmission operations and requires coordination with the reliability coordinator. 

Commit Capacity Resources -- Prior to committing the generating units to meet these energy requirements, a predefined amount of operating reserves is added to the projected energy requirements. Then the generating units are committed to meet these requirements (including reserves) for the next 24 to 96 hours based on discussions with the generating stations to determine their availability. This step is referred to as Unit Commitment. 

Develop Transactions with Other Power Producers  -- Normally, after committing the units and determining whether there is access capacity available for sale or there is a need to purchase to cover a deficiency in generating capacity, an individual then goes to the market and sells the excess or purchases the deficiency. These transactions are reviewed by the interchange authority. 

Advanced Tools for Power System Operator 

SCADA -- Analog information is gathered from remote terminal units from substations throughout the system by the SCADA scanning program. This information is made available to you through real-time and study versions of diagrams and tabular displays. 

Power System SCADA

Information includes bus voltages, line flow, and transformer flow and transformer oil temperature. With the newest control systems you will have physical control of essentially all controllable apparatus and functions. SCADA means supervisory control and data acquisition. 

Power System Simulators -- Energy management computer systems have other tools available to assist in performing your duties. These tools include mathematical models of the transmission system such as power flow studies, contingency evaluation studies and state estimation programs. 

Power System Simulators

The state estimation program, which calculates unknown system values, checks actual metered values for relative accuracy and calculates unknown metered quantities and is the most useful tool today. In addition, to avoid major outages, operating guides based on detailed studies, are also available to the system operator and outage coordinator. These operating guides are reviewed and approved by the reliability authority prior to being made available for use by the system operator. 

System Controllers -- Control functions are available to you as the system operator. Using the one-line diagrams and tabular displays and these control functions, you have ability to turn breaker and automatic reclosure on or off, control first and second end reclosing, and turn transfer trip relaying on or off.