Implementation of protection system used in high power transformer rating protection
CHAPTER ONE INTRODUCTION
The purpose of an electrical power system is to generate and supply electrical energy to consumers. The system should be designed and managed to deliver this energy to the utilization points with both reliability and economy. Many items of equipment are very expensive, and so the complete power system represents a very large capital investment. To ensure the maximum return on the large investment in the equipment, which goes to make up the power system and to keep the users satisfied with reliable service, the whole system must be kept in operation continuously without major breakdowns and also to reduce the impact of fault on the other parts of the system.
The importance of the protection lies in two basic points :
1- Detect faults and identifies how serious they are and where are their places. 2- Isolate the affected elements faults and opening the appropriate cutouts.
Protection System a complete arrangement of protection equipment and other devices required to achieve a specified function based on a protection principal.
Protection Scheme: a collection of protection equipment providing a defined function and including all equipment required to make the scheme work (i.e. relays, CT’s, CB’s, batteries, etc ).
Relays are the devices, which monitor the conditions of a circuit and give instructions to open a circuit under unhealthy conditions .
The basic parameters of the three-phase electrical system are voltage, current, frequency and power. All these have pre-determined values and/or sequence under healthy conditions. Any shift from this normal behavior could be the result of a fault condition either at the source end or at the load end .
Transformers are a critical and expensive component of the power system. Due to the long lead time for repair of and replacement of transformers, a major goal of transformer protection is limiting the damage to a faulted transformer. Some protection functions, such as over excitation protection and temperature-based protection may aid this goal by identifying operating conditions that may cause transformer failure. The comprehensive transformer protection provided by multiple function protective relays is appropriate for critical transformers of all applications.
A protective relay is the device, which gives instruction to disconnect a faulty part of the system. This action ensures that the remaining system is still fed with power, and protects the system from further damage due to the fault. Hence, use of protective apparatus is very necessary in the electrical systems, which are expected to generate, transmit and distribute power with least interruptions and restoration time. It can be well recognized that use of protective equipment are very vital to minimize the effects of faults, which otherwise can kill the whole system. Relays may be classified according to the technology used :
- Electromechanical relay: They work on the principle of a mechanical force causing operation of a relay contact in response to a stimulus. The mechanical force is generated through current flow in one or more windings on a magnetic core or cores, hence the term electromechanical relay and this relay can be classified into several different types as follows: attracted armature, moving coil, induction, thermal, motor operated, mechanical .
- Static relay: This term implies that the relay has no moving parts, Their design is based on the use of analogue electronic devices instead of coils and magnets to create the relay characteristic. Early versions used discrete devices but advances in electronics enabled the use of linear and digital integrated circuits
- Digital relay: In this type Microprocessors and microcontrollers replaced analogue circuits used in static relays to implement relay functions .
Statement of problems
Faults occur in substation will eliminate the services from the units for this reason effective protection action is required to minimize damage and repair costs where it senses fault, Ensure safety of personnel.
The main objectives of this research are to develop and investigate protection system used in high power transformer rating protection.
The first stage in this project; numeric relays from ABB techniques used to obtain protection transformer. This protection using ABB REF615 which protect over current, restricted earth fault and differential protection.
On second stage selected setting of numerical According to IEEE Standers and ABB Technical guides.
On final stage run simulation to test the setting.
The thesis is organized as follow :
Chapter one gives brief introduction about relay in protection in electrical network and summarized research objectives and problem.
Chapter two contains introduction about electrical section. Also contains detailed understanding to protect the transformer.
Chapter three contains the of numeric relay Hardware ,Relay interfaces and algorithms.
Chapter four testing of numerical relay with simulation before and after connection to transformer.
Chapter five conclusion and recommendations.