Measures taken for ultra-short lines

With the completion of Maanshan Iron & Steel's 2500m / h oxygen generator and other major projects, large-scale production equipment continues to increase, the equipment's stand-alone capacity continues to upgrade, and power facilities have also made major breakthroughs in equipment. The capacity of the single-unit transformer has reached 120MVA, and the single-machine capacity of the synchronous motor introduced by the company has reached 32MW. Does Magang currently consume 5.5 million kW of power? About h, how to ensure that the production plant and mine are running forward, the normal supply of power medium is the key, and the important part of the power protection is the top priority. The safe and reliable operation of the relay protection device and the correct action rate of the automatic device have become our key tasks Subject.

1 The status of Magang's power system protection devices 2.1 Traditional protective devices occupy an important position Magang has 21 substations of various voltage levels, which were built in different periods, and the relay protection devices can be divided into about 5 categories: (1) Electromagnetic Types such as: DL series, GL series, etc .; (2) Rectifier type (3) Transistor type (4) Integrated circuit type (5) Microcomputer protection type These types of protection devices have played special roles in different stages of the development of Magang. Due to the development of Magang Power Grid, the layout is not as standardized and structured as the new-type enterprises. It is a trajectory of pin-type development. The layout of the station is not reasonable enough, and there are some problems in the system.

2.2 Existing problems Ma Steel's power system presents the following characteristics on lines and equipment: there are many ultra-short lines within.

(2) There are many multi-load T connections on long lines.

(3) In overhead lines, there are many transition cable connections.

(4) There are many middle ends of the cable line, so there are many faults.

(5) The primary equipment is old and the insulation is not ideal (exceeding standard operation).

(6) Some devices (such as cross-linked cables) have no means of testing and inspection, and hidden dangers are not easy to find.

These weak points where the power system is prone to problems are a test for the correct operation rate of the relay protection device. The traditional electromagnetic protection and other protection also bear the protection function of most equipment. It is difficult to meet the selectivity of the protection device in the configuration of the current grid structure, the accuracy of the fixed value coordination, and the following problems in protection: (1) Non-selectivity in short-time protection level difference coordination.

(2) The coordination of one type of quick-action protection and another type of quick-action protection is difficult. For example, when the 110kV 815 line fails, the longitudinal difference of the 815 metallurgical power line and the 871 line zero-sequence section I are simultaneously tripped, as shown in Figure 1. As shown.

Due to the particularity of the operating conditions of the metallurgical system, the pollution is more serious. The auto-reclosing of the Maanshan Iron and Steel Power Grid has not been put into operation, and the phenomenon of pollution flashover has occurred from time to time. There are many secondary wiring inside the traditional protection device, and the secondary wire insulation is damaged The fall, the failure of the relay element, the breakdown of the terminal insulation, and the looseness of the connection cause the system to trip. These abnormal protective actions pose a serious threat to the company's production.

The measures taken are aimed at the problems left over by history. While increasing the technological transformation, our factory has taken the following measures: (1) Strengthen the learning of the commissioning staff's business skills.

(2) Commission and inspect the device in strict accordance with the regulations.

(3) Ensure that the commissioning cycle is implemented, strengthen patrol inspection, and strictly inspect the connection points of the secondary circuit in accordance with standard operations, and take responsibility to the person.

(4) Ensure the operating environment and conditions of the relay protection device.

After all, the above-mentioned main measures are realized by people. With the development of microcomputer technology and communication technology, microcomputer protection is moving forward at a rapid pace, and the performance-price ratio of microcomputer protection is also continuously improving. Its characteristics are specifically manifested in: (1 ) It can integrate the overall functions of main protection and backup protection into one, and realize completely independent double protection on high-voltage lines, large and medium-sized motors and important power equipment.

(2) Remote communication function, the management personnel can monitor the running status of the protection device at any time, call the data, change the fixed value, and provide the necessary conditions for modern management.

(3) Self-checking function, automatic fault location, instant alarm, replacement of faulty parts with spare plug-ins.

3 Protection system in large equipment The realization of microcomputer protection makes it possible to achieve comprehensive automation of the system. Years of operating experience and practical lessons require that power system managers must get rid of traditional concepts as soon as possible and apply modern automation technology. This is the safety of Ma Steel ’s power system. Guaranteed operation.

3.1 The static modular GSX10 protection system 32MW synchronous motor of the blast furnace blower unit adopts the protection system introduced by the company. This system is a comprehensive product of traditional protection devices and microcomputer protection. It is an intermediate product between traditional protection and microcomputer protection. It protects The relay is divided into three groups, each group is equipped with independent DC power supply and matrix unit, and is equipped with test device and signal module, relay action and trip monitoring start module.

The FC95 frequency relay and MC91 multi-function relay in the GSX10 protection system have a microprocessor function. The setting parameters can be called and set through the device panel buttons, and the desired value can be read intuitively on the LCD screen, but there is no fault record Wave and event recall function.

The multifunctional relay contains: (1) overcurrent and quick break; (2) negative sequence and zero sequence; (3) overheating and other conventional protection functions.

Differential relays in the protection system, GIX104100% fixed, rotor grounding relay, PPX105 power relay, EPX103 impedance relay, uT91 voltage relay are all integrated circuit type protection devices, their settings can be conveniently set by dial switch or rotary contact locking.

When a protection device in the GSX10 protection system sends out an action signal, it is quickly sent to a trip or other control loop through the trip matrix AL90 or the blocking matrix EL90, so as to achieve the purpose of program control.

3.2 Sepam series multi-function microcomputer protection system oxygen generating station, oxygen compressor, nitrogen compressor and air compressor, 40MVA transformer and other main equipments are all adopting Sepam series decentralized microcomputer protection device introduced by Meiri Meilan Company.

It has: (1) protection; (2) measurement; (3) three major functions of program logic, and efficient and accurate self-diagnostic system software, which can continuously check the working status of the three major functions to ensure that the protection function is always in normal and intact The running state, this online self-diagnosis method improves the reliability of the correct action of the protection device, which is one of the important differences that cannot be achieved by other protections on the Ma Steel Power Network.

The protection function includes all the contents of power equipment protection. It integrates line protection, main transformer protection and other contents in one body, and its applicability is quite strong. Its characteristics basically meet the requirements of microcomputer protection at the current stage. The programmer is inserted into the RS-communication port, and according to the logic state of the input and output signals, the faulty circuit and corresponding components can be quickly and accurately detected.

The system can accurately record the current and voltage parameters during the fault, and store the fault amount, which is convenient for the protection personnel to analyze the fault after various accidents and provides a basis for the qualitative fault. In the case of equipment authorization (enter password), non-professionals cannot enter the parameter modification program, which provides a guarantee for the reliable operation of the protection device.

4 Some considerations on the current status of Maanshan Steel's protection devices 4.1 Increase technical innovation and obtain operating experience as soon as possible In a short period of time, we must fully realize the transformation of 21 stations. No matter in terms of funds, metallurgical power is an advanced feature to improve users' functions. Technical measures.

4 Research and discussion of several issues 4.1 The relationship between protection and monitoring In the application of the actual enterprise distribution network, there are two main ways to connect the microcomputer protection and monitoring part of the substation integrated automation system. One is to monitor the network through the serial port of the protection device, and the second is to set up one (or more) protection management machines to manage all the protection devices, and then the protection management machine and the monitoring system are networked.

Although many substations adopt the first method for integrated automation, the author believes that the second method is better.

4.2 Protocol standardization and openness of the system It is very important to adopt standardized data transmission protocols between the relay protection device of the automation system and the substation control system. At present, there is no unified standard on the data transmission protocol for substation automation systems on the domestic market, and even a system from a manufacturer is also a few protocols, so the standardization process of the protocol should be accelerated.

For the first protection and monitoring connection mentioned in Section 4.1, it is easy to implement products that belong to the same manufacturer for protection and monitoring.

It is more difficult for products of different manufacturers to achieve communication connection. For the second method, even if the protection and monitoring products do not belong to the same manufacturer, or there are several protection products in the same substation, it is easier to achieve communication connection.

4.3 Remote modification of protection setting value At present, most domestic manufacturers claim to users that their system can modify the protection setting value from a distance, but the operation practice shows that this method is also insufficient. Once the protection is refused or malfunctioned due to the change of the setting value, it is difficult to distinguish The responsibility is to protect itself or to dispatch or teleport. On the contrary, foreign systems (such as the German LSA678) are not allowed to modify the protection settings randomly from a remote location, and only allow the protection settings to be switched from a remote location. That is, several sets of settings are stored in the protection unit in advance, which can be switched from a distance. Learn from domestic manufacturers.

5 Conclusion The substation is an important link in the power system, and its normal operation is an important factor for the safe operation of the power system, in order to ensure the high-quality, safe and economic operation of the substation. Its monitoring, control and protection technology is becoming increasingly important. The substation integrated automation system has been developed to meet this requirement and has gradually become the focus and admiration of enterprise managers.

Substation comprehensive automation as a subsystem of power grid dispatching automation should be subject to the overall design and requirements of power grid dispatching automation. The configuration and functions of its automation system, including the arrangement of equipment, should meet the requirements of power grid safety, high quality, economic operation, and hierarchical information transmission. And information sharing principles.

1 Golden Meridian Bridge. Development strategy of substation automation system. Power supply, Huang Xiaoli, 1998.42. Grid modernization management and grid automation. China Power, Min Guiqin, 1997.13. The application of integrated automation in unattended substations. Power system automation, 4 Zhu Anli, Shuai Junqing. About the functional requirements of the 110kV and 35kV substation integrated automation system. The power grid technology is unrealistic in 1997.1 or the specific link of implementation (load distribution), but the application of microcomputer protection devices of manufacturers with excellent performance, mature products and mature operation experience in the demonstration station should be urgent.

4.2 Reasonably configure the current protection to ensure the selection of important lines 815 line and 871 line as two adjacent short lines, and change the 871 zero sequence I constant speed section to the line longitudinal difference as the main protection to meet the selectivity and avoid 871 line zero sequence section I extended to 815 line has achieved selective requirements.

4.3 Reasonable setting of reclosing and automatic switching devices For heavily polluted areas and through mountain forest lines, reasonable setting of automatic reclosing devices is very beneficial. In recent years, Ma Steel has caused several trips on 110kV lines due to pollution flashovers. This transient failure should be an effective way.

4.4 Reasonable configuration of UPS power supply device Due to the voltage fluctuation, the low voltage contactor of the production plant and mine and the computer control system are out of control, which is quite common in recent years. Each production unit should account for the capacity of important loads that cannot lose power, and configure UPS power sources reasonably to ensure production continuity. In this respect, 2500m blast furnace blast station system has mature experience in operation.

5 Conclusion The progress of an enterprise is supported by technology. Despite its unique advantages, microcomputer protection is unmatched by traditional protection, but it cannot be generalized in metallurgical enterprises. It is still economical to install or retain some traditional protection on some unimportant loads. Significance. At present, the equipment and staff quality of enterprises are still in a state of unevenness. It is the direction of the work to carry out technological transformation in different levels, step by step, and brisk walking.

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