Directional Relaying and Distance Relaying - PDF

Topic 7&8: DIRECTIONAL RELAYING & DISTANCE RELAYING Report by Group 4 Arcano, Marcellinus T. Ayson, Maricel D.S. Nuguid, Wiljhay Pelayo, Reyster Brix R. Robles, Kesiah Rae V.  WHAT IS RELAYING? Relaying is the branch...

Topic 7&8: DIRECTIONAL RELAYING & DISTANCE RELAYING Report by Group 4 Arcano, Marcellinus T. Ayson, Maricel D.S. Nuguid, Wiljhay Pelayo, Reyster Brix R. Robles, Kesiah Rae V.  WHAT IS RELAYING? Relaying is the branch of electric power engineering concerned with the principles of design and operation of equipment (called ‘relays’ or ‘protective relays’) that detects abnormal power system conditions, and initiates corrective action as quickly as possible in order to return the power system to its normal state. The quickness of response is an essential element of protective relaying systems– response times of the order of a few milliseconds are often required. Consequently, human intervention in the protection system operation is not possible.  WHAT IS DIRECTIONAL RELAY? A Directional Relay in electrical engineering is a protective device used in power systems to identify the direction of fault currents and isolate the damaged segment of the system while keeping the remainder of the network functional.  WHAT IS DIRECTIONAL RELAY? Directional overcurrent relays respond to excessive current flow in a particular direction in the power system. The relay typically consists of two elements. A directional relay is an element, which determines the direction of current flow with respect to a voltage reference.  Feeder Protection: Directional relays protect radial and parallel feeders from faults such as short circuits, ground faults, and overloads. WHAT IS DIRECTIONAL RELAY? WHAT IS DIRECTIONAL RELAY? Potential Transformer (PT) Section: This portion includes a potential transformer, which reduces the voltage of the power system to a level that the relay can process. Current Transformer (CT) Section: This part has one or more current transformers that reduce the current flowing through the power supply to a level suitable for the relay to manage. WHAT IS DIRECTIONAL RELAY? Potential Coil: The potential coil, also called the voltage coil, is a winding inside the relay that receives the voltage signal from the potential transformer. Current Coil: The current coil, also known as the directional coil, receives current signals from the current transformers. WHAT IS DIRECTIONAL RELAY? To Trip Circuit Section: This section describes the mechanism for tripping the circuit breaker when a fault is identified. The directional relay identifies whether the fault is in the forward or backward direction by comparing the voltage and current signals received from the potential and current coils. If a failure is identified in the forward direction, the relay transmits a trip signal to the circuit breaker, which isolates the faulty component of the system.  Transformer Protection: Directional relays guard against internal faults and external faults on connected transmission lines, working in conjunction with other protective devices like differential relays. Generator Protection: Directional relays protect generators from faults that may occur within the generator or on connected transmission lines.  WHAT IS DISTANCE RELAY? Distance relays - are the protecting equipment that functions based on the distance of the fault point on the transmission line. The distance is calculated from the generating unit. Based on the distance, the impedance is calculated by evaluating the fault voltage and fault current.  DISTANCE RELAY WORKING PRINCIPLE The distance relay working principle is very simple and it is based on the ratio of voltage and current i.e, impedance. This relay contains a potential transformer to supply voltage and current transformer for the current element, which is connected in series with the entire circuit. The secondary current of CT produces the deflecting torque whereas the potential transformer produces restoring torque. As we know that its operation depends on the ratio of voltage and current ie, the ratio of impedance value, which is also known as impedance relay.  DISTANCE RELAY WORKING PRINCIPLE Distance relaying is commonly used for: 1. Protection of transmission lines 2. Transformers 3. Busbars in modern power systems It is particularly useful for detecting faults on long-distance lines, as it can estimate the physical distance between the relay's sensing transformers and the fault location. EXAMPLE OF DISTANCE RELAY WHAT IS DISTANCE RELAY? Relay Construction: The time distance impedance relay includes a current-driven element, such as a double-winding type induction overcurrent relay. Its mechanism involves a spindle with a disc, connected via a spiral spring to another spindle that manages the relay contacts. An electromagnet, energized by the circuit’s voltage, holds these contacts open under normal conditions. WHAT IS DISTANCE RELAY? - The voltage transformer measures the voltage across the protected equipment - The current transformer measures the current flowing through it - The sensing unit then calculates the impedance based on these measurements and compares it against predefined thresholds - If the impedance exceeds these thresholds, the relay will trip, sending a signal to the circuit breaker to isolate the faulted section of the system. WHAT IS DISTANCE RELAY? - The relay measures the impedance of the faulty point. If the impedance is less than the impedance of the relay setting, it gives the tripping command to the circuit breaker for closing their contacts. The impedance relay continuously monitors the line current and voltage flows through the CT and PT respectively. If the ratio of voltage and current is less than the relay starts operating, then the relay starts operating. -  REFERENCES DIRECTIONAL RELAY https://testbook.com/question-answer/directional-overcurrent-relay-is-used-for-the-prot--5fb4f190f952d03248dd2b41 WHAT IS DIRECTIONAL RELAY? https://polynoteshub.co.in/what-is-directional-relay/ FEEDER PROTECTION https://circuitglobe.com/feeder-protection.html DIRECTIONAL RELAY WORKING PRINCIPLES https://www.electricity-magnetism.org/directional-relay/ WHAT IS DISTANCE RELAY, TYPES & CHARACTERISTICS https://www.watelectronics.com/what-is-a-distance-relay-types-its-characteristics/ DISTANCE RELAY APPLICATIONS http://elprocus.com/what-is-a-distance-relay-working-its-applications/