F650-N-F-L-F-2-G-1-HI-P-6E Protection Relay – GE

Description

Load Encroachment

Feeders may experience very heavy load increases due to various contingency situations. The Load Encroachment function in F650 provides the capability to manage such load growth in feeders. The load encroachment element can be set for the feeder’s expected maximum load, reducing the likelihood of false tripping for load conditions while maintaining dependability to trip for legitimate faults. The load encroachment supervision in F650 is based on positive-sequence voltage and current and applies a characteristic as shown in the figure above. It allows the user to set the phase overcurrent elements below peak load current to see end-offline phase faults in heavily loaded feeder applications.

Advanced Automation

The F650 incorporates advanced automation features including powerful programmable logic, communication, and SCADA capabilities that far surpass what is found in the average feeder relay. The F650 integrates seamlessly with other Multilin relays for complete system protection.

F650 Logic Configuration

F650 Logic Configuration is the powerful programming logic engine that provides the ability of creating customized protection and control schemes thereby minimizing the need, and the associated costs, of auxiliary components and wiring. Using F650 Logic Configuration, the F650 can be programmed to provide required tripping logic along with custom scheme logic for auto transfer schemes (Main-Tie-Main), load shedding based on frequency, voltage and communication, loop restoration schemes, other remedial action schemes and dynamic setting group changes. F650 provides a comprehensive set of analog operands for two digital or analog inputs.

Due to the difficulty in measuring the amount of coal entering the furnace, a method for calculating the efficiency of a counterbalance boiler has emerged. When using the counterbalance calculation method, the problem of directly measuring the amount of coal entering the furnace should be avoided. Instead, the useful heat produced by the boiler should be directly measured, while the heat loss of the boiler should be measured, including exhaust loss q2, chemical incomplete combustion loss q3, mechanical incomplete combustion loss q4, slag discharge (fly ash and slag) loss q5, heat dissipation loss q6, and conversely, the method of calculating the amount of fuel entering the furnace is called the “counterbalance method”. In the calculation of q3~q6, the main reliance is on laboratory data and empirical coefficient estimation. Q2 is calculated by measuring the excess air coefficient of flue gas and using data from fuel composition analysis to calculate the theoretical flue gas volume, calculate the flue gas volume, and multiply it by the exhaust temperature. Therefore, according to the counterbalance method, the boiler efficiency is: η K=(ql/ql+q2+q3+q4+q5+q6) XlOO% In this method, although there are many empirical coefficients that make the accuracy of the counter balance calculation low, it avoids the frequent testing of the coal input and fuel heat generation. In theory, the error is considered to be less than the positive balance error, which is estimated to be around 1% under general thermal experimental conditions.
In recent years, in large thermal power generation units, direct blowing systems such as medium speed coal mills or double inlet and double outlet steel ball mills have been widely used, and metering coal feeders that can accurately and timely measure the amount of fuel entering the furnace have been equipped, greatly improving the accuracy of positive balance calculation and allowing continuous measurement. Relevant data is directly fed into the combustion regulation and DAS systems. In this case, some have proposed using positive balance instead of negative balance in the DCS system.

In actual project operation, even if DCS is equipped with positive balance calculation software, end users often demand not to abandon the calculation method of reverse balance. The reason for this is due to the following reasons: A. End users’ requirements for DCS performance calculation software often not only meet the needs of reports, but also hope to provide economic operation guidance for operators. For example, it is necessary to know the extent to which changes in parameters affect boiler efficiency; How to adjust the parameters of the unit under what operating conditions to maintain the best economic operating state of the unit, etc. The original operating parameter settings were obtained through thermal tests and accumulated operational experience. During actual boiler operation, the situation often undergoes many changes. Adopting positive balance, unit efficiency is equivalent to only calculating one general ledger, which is not conducive to analyzing changes in unit operating conditions. The counterbalance method can relatively conveniently find ways to improve the operation from various heat losses. B. The various indicators of counterbalance are intuitive, easy to operate and compare, and the so-called “small indicators” for operation are the assessment indicators for the economic operation norms of Chinese power plants. Therefore, in actual DCS design, two types of algorithm software are often configured to meet the requirements of the end user. However, end users are still often dissatisfied. This includes both requirements for calculation accuracy and other aspects. There are reasonable requirements and areas for discussion, and this article will discuss this issue.

The basic calculation principle of steam turbine efficiency is to measure the heat entering the steam turbine system minus the recovered heat sent back to the boiler and other auxiliary systems, and remove the heat converted from the useful power of the generator to obtain the efficiency of the steam turbine. Large units all have reheating systems. The measurement of reheat steam flow rate poses certain difficulties in calculating the heat entering the steam turbine thermal system due to the inability to install flow measurement (throttling type) devices in the reheat system. In the past, traditional methods used to measure the drainage flow rate of # 2 high pressure heater and calculate the reheat steam flow rate in certain key parts. Some recently constructed projects utilize the strong computing power of the DCS system to calculate the extraction flow rate, heater efficiency, and condenser efficiency based on the enthalpy difference between various stages of extraction steam and heaters according to the condensate flow rate, in order to calculate the reheat steam flow rate and turbine efficiency. This method, similar to the counterbalance method of boilers, is also widely accepted by end users. When it is impossible to install measuring devices for the flow rate in some parts, such as steam for shaft seals, certain pipelines in drainage systems, etc., appropriate correction should be considered. The enthalpy of chemical makeup water and the steam consumption of steam driven feed pumps cannot be listed as constants in efficiency calculations.