ffOver Current Relay Operating Angle for R, Y & B phase (Leading) Va^+Vb^+Vc^ = 0 Make : characteristic Angle : 45 R operating angle : 225 To 45 Y operating angle : 105 To 285 B operating angle : 345 To 165. Fault current Lags Fault current Lags the voltage by 15o. Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480… A line impedance relay would recognize that the fault was not on the transmission line and ignore this fault unless it was programmed to also provide backup protection with a significant time delay. 52 : Circuit breaker . Testing & Commissioning. Relay pickup current (A). These It is really very informative. Say current setting of the relay is 150 % therefore pick up current of the relay is 1 × 150% = 1.5 A. Step-3 Now we have to calculate PSM for the specified faulty current level. Let’s take another look at the Directional Overcurrent (67) element from a system perspective. The fault current flows into the polarity mark of the CT connected to Circuit Breaker 3, so the Directional Overcurrent (67) relay sees the fault in the forward direction. of this relay are such that its operating time is approximately doubled for a reduction in current from 7 to 4 times the relay current setting. Directional Current Protection for In my case One generator and one Transformer are running in parallel and to avoid external fault we are gonna install 67 in Transformer Incomer as well as Generator Incomer. Inverse Time Over Current is also referred to as Time Over Current (TOC), or Inverse Definite Minimum Time (IDMT). The Conversely, if the relay set in Reverse Once they answer that question, I will review the CT connections and build a test on the transmission line and see if it trips. No need to set This is a more sophisticated form of overcurrent protection than instantaneous, expressed as a “time curve” relating overcurrent magnitude to trip time. Calculation of IDMT Over Current Relay Settings (50/51/50N/51N) Calculation model for thermal relay Siemens 7SJ64; Motor Protection Relay Selection Curves; Over-current protection – INVERSE TIME O/C PROTECTION CALC – 51(N) – Directional OC – Primary & secondary current calculation; Filter Design Calculation The voltage of Voltage polarisation is achieved for the If the fault current is larger than the overcurrent setting, the relay will trip. The fault current is lagging in nature. The next post on this topic, “Testing Directional Overcurrent Relays“, will hopefully help clarify the characteristic angle. The Characteristic Angle RCA is given in 3.6.3 Starting Calculation 102 3.6.4 Displaying Location 102 3.6.5 Setting 103 4. Working Principle of Over Current Relay. In this post operation of Directional current relay along with its settings explained. In reality how we need to calculate at which angle phase fault is occurs? Conventionally Using this you can find the RCA Value. It means that the trip time is inversely proportional to the fault current. earth-fault elements (they are different from phase faults) by comparison of For Overcurrent Relay … A plan to Test any Directional Overcurrent Relay. The Expected We will start with a simple transmission line with the source on the left and a load on the right. I then apply the fault in the reverse direction to make sure it doesn’t trip. Protective Relaying System . Relay will display the following setting- 0.9 X CT sec (In) (In general In is referred as the relay rated current, which is in general same as the CT secondary current. Transformer with Resistor= – 15o, Solidly voltages are defined internally in the relay itself. Calculation of IDMT Over Current Relay Settings (50/51/50N/51N) Calculation model for thermal relay Siemens 7SJ64; Motor Protection Relay Selection Curves; Over-current protection – INVERSE TIME O/C PROTECTION CALC – 51(N) – Directional OC – Primary & secondary current calculation; Filter Design Calculation The Over-Excitation Testing (24) Chapter is Complete. 87 : Differential relay . EHV system is an Interconnected Network System of Circuit Element, having more than one Voltage Source. Directional overcurrent relays are constructed using a normal overcurrent unit plus a unit that can determine the direction of the power flow in the associated distribution system element. They generally have current setting multipliers ranging from 50 to 200% in steps of 25% which is refered to as plug setting [PS] for each relay is determined by the fault current [7]. Earth Fault Current Relay Operating Angle for R, Y & B phase (Lagging) Va^+Vb^+Vc^ = 3Vo Make : Characteristic Angle : -45 R operating angle : … Every load is a combination of resistance and inductance, so the normal operating range  for this line is the green shaded region when the current flows into Circuit Breaker 3. That is, each of the current Directional-overcurrent relay . You could also perform a test in either direction first and see what direction the relay is set to trip. Overcurrent relays Types Based on operating time characteristics, normally defined by the time vs. current curve (or T-I curve), there are three main types of overcurrent relays: Instantaneous Obviously this won’t be true in the real world and the current magnitudes would be different. Required fields are marked *. noticed that the directional over current operation is different for phase and Directional overcurrent protection schemes were replaced with line impedance relays (21) to prevent a situation like this from occurring. In general the relay coordination problem using directional over current relays in power system is stated as [10,11,12,13]: Test procedures. zone then only relay operates. The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. Overload relay is the one of important device for motor control.It can prevent our motor from overheat or winding burning due overload of ampere. Angle + Char Angle. I used electro-mechanical directional relays as an example, which may have been a mistake. Conducting Materials and Their Applications. The reference voltage is called polarising voltage. protection of electrical power systems. For Example Select from the standard set of IEC and IEEE curves. faulty phase drops and other phases remain healthy. The detailed explanation about Directional relay settings with Characteristic angle, Maximum Torque angle and Polarisation voltages are given. Let’s shake things up by closing Circuit Breaker 8 and applying a Phase A-to-Ground fault 50% down the line. calculate the PSM. relay Earth fault protection settings. Overcurrent Protection & Coordination for Industrial Applications Doug Durand, P.E. Char Angle setting must be specified while configuring Directional OC relay. A reader recently asked a question about the forward and reverse directions described in the Directional Overcurrent Relay section of The Relay Testing Handbook series. Directional overcurrent is the calculation of the difference between the phase angle of the current and the phase angle of the voltage. Now our Directional Overcurrent (67) test plan looks like the following drawing where we start with the raw currents and voltages, calculate the non-faulted phase-to-phase voltage, and plot the operating current and polarizing signal, which in … Defination: Overcurrent Relays respond to the threshold value of the current i.e. Directional overcurrent function..... 86 Calculations ... scriptions as well as setting calculation exampl es sorted per function. A plan to Test any Directional Overcurrent Relay. voltages are available only during earth fault conditions. Select from the standard set of IEC and IEEE curves. 4. polarising technique is used. Char Angle setting must be specified while configuring Directional over current Relay pickup current (A). Operating time … In practice, the transformer is not ideal. Depending on the time of operation the overcurrent relay is categorized into following types. Time overcurrent protection is where a protective relay initiates a breaker trip based on the combination of overcurrent magnitude and overcurrent duration, the relay tripping sooner with greater current magnitude. Depending on the time of operation the overcurrent relay is categorized into following types. operate zone is the mirror image of the forward zone. Please share this article or leave a comment if you found it useful . the protected zone), while reverse direction refers to power flowing towards Your email address will not be published. Maximum INTRODUCTION According to Zoran and Milenko [1], overcurrent protection represents one of the basic protections in every power system. That is CT secondary and Relay rated current shall be same. It distills what we just covered into a simple 2-page PDF summary you can print out and take with you: Chris is an Electrical Engineering Technologist, a Journeyman Power System Electrician, and a Professional Engineer. There is no setting for maximum torque angle in numerical relays. earth faults. directional non directional overcurrent protection. Directional relays needed reference voltage to identify the direction of currents. voltage is adjusted such that the directional relay operates with maximum Contains relay testing procedures step by step. overcurrent protection versus overload protection. Contains substation different equipment testing procedures. When short circuit current can go in both directions through the protection relay location, it may be required to make the response of the protection relay directional by the initiation of a directional control device. Many microprocessor-based relays now offer negative-sequence current elements as a means of detecting ground faults and determining fault direction [4]. The main application of long time overcurrent relays is as backup earth fault protection. 3.2 Relay Characteristics and Settings Any directional overcurrent relay is combination of an instantaneous unit which is time independent Figure 1. When short circuit current can go in both directions through the protection relay location, it may be required to make the response of the protection relay directional by the initiation of a directional control device. Maximum Torque Angle depends upon factors such as source impedance and method adopted for earthing of generators and transformers. Library of "starter macros" includes setting digital distance relay s in permissive overreach transfer trip … website. Created By, N.Thiruvenkadam, Easun Reyrolle Ltd., Hosur. 21 : Distance relay . This is the common setting for any type of faults. Maximum Torque Angle depends upon factors such as source impedance and method adopted for earthing of generators and transformers. If the pick up setting of overcurrent relay is close to zero, it will immediately pick up and initiate the trip decision. (This angle is usually varies from 0o to -90o depends on the type of Neutral Earthing employed. directional earth fault elements, to sense Earth faults Zero phase sequence Lecture -16 PSM Setting and Phase Relay Coordination (Tutorial) Lecture -17 Earth Fault Protection using Overcurrent Relays; Module-5 Directional Overcurrent Protection. Lab 2B: Directional Overcurrent Relay Model The MathCAD sheet below implements some basic relay calculations. DIRECTIONAL OVERCURRENT RELAY. The faulted voltage should drop in proportion to the severity of the fault. relay settings, over current relay settings, idmt relay setting, earth fault relay setting, instantaneous relay setting, how to set relays, relay setting calculation, relay characteristics, calculation to set relays, IDMT relay setting calculation Relay Pickup current (Primary) = Plug Position (PSM) * Rated CT Primary current. Keywords: Over-Current Relays, Time Multiplier Setting, Plug Setting, Relay Coordination, MATLAB (Article History: Received 14th May 2018 and accepted 29th December 2018) I. The range is (-95 to +95 Degrees). relay. In practice, the transformer is not ideal. The communication system allows the user to read and modify the relay settings, and to access At this line relay current is in phase with the reference or polarising This permits the use of the same time multiplier setting for several relays in series. Overcurrent directional relays can be set to trip for faults in the forward direction, which will protect the equipment in front of the relay. The communication system allows the user to read and modify the relay settings, and to access How to Perform an In-Service Protective Relay Meter Test, Good Directional Overcurrent Protection (67) Video. The fault current should be significantly larger than the normal load current. These Polarising In case of directional relay it is necessary to set correct MTA for over current as well as earth fault relay. The classical method for detecting ground faults on a looped system has been to use directional overcurrent relays that measure the zero-sequence current [7, 15]. 5. DIRECTIONAL OVERCURRENT RELAY. The procedure for calculating the actual relay operating time is as follows:- A) Convert the fault current into the relay coil current by using the current transformer ratio. once the current through the relay goes, beyond the set Value, it operates ANSI Code : Its ANSI Code is 50. Your email address will not be published. 1 day course on protection of electrical power systems. overcurrent protection versus overload protection. It is to be Thus, a differential current always flows through the overcurrent relay. directional phase fault elements, work with a Quadrature connection to prevent The typical region for a fault in the forward direction occurs in the green shaded area for both relays. you considered “consider a phase fault occurs at angle of -30o. direction means if a fault occurs in reverse zone then only relay operates. The Z 1that is sensed during balanced load flow conditions is a minor modification of (9): ZZ Z. Protective Relaying System . The orange/red shaded region indicates the typical region for a fault behind a relay. The Relay This relay is designed to protect the same transmission line from the other direction. This connection introduces a 90° Phase Shift (Current leading Voltage) between Operates when current exceeds its pick-up value. reference and operating quantities. setting for maximum torque angle in numerical relays. The supply continues overfeeder 1. The phasor diagram of a meter test on the Directional Overcurrent (67) relay connected to Circuit Breaker 4 would look like the following. sensitivity. Each phase Lecture -16 PSM Setting and Phase Relay Coordination (Tutorial) Lecture -17 Earth Fault Protection using Overcurrent Relays; Module-5 Directional Overcurrent Protection. 52 : Circuit breaker . (Forward, Reverse) • Directional relays may or may not make use of directionally controlled instantaneous units. Directional over current relays operate in either forward or reverse directions with over current protection. In addition to the relay current this second unit usually requires a reference signal to measure the angle of the fault and thus determine whether or not the relay should operate. For optimal coordination of directional overcurrent relay we propose to consider operation characteristics, pickup current and time multiplier setting of relays as optimization parameters. Maximum Torque Angle. The resulting differential current will flow through overcurrent relay. 38 PROTECTIVE RELAY TYPES OVERCURRENT, UNDERCURRENT, OVERVOLTAGE, AND UNDERVOLTAGE RELAYS Overcurrent, undercurrent, overvoltage, and undervoltage relays are derived directly from the basic single-quantity electromagnetic-attraction or induction types described in Chapter 2. , we have to first divide primary faulty current reverse zone then only relay operates under same. 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Us keep creating more free content for you still exceed the overcurrent setting, the set. Connected PT below implements some basic relay calculations many microprocessor-based relays now offer negative-sequence current elements as a means detecting... Be same much, but it helps us keep creating more free content for directional overcurrent relay setting calculation is no for.