Protective Relay Calculations and Settings. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. applications. calculation: IDMT Characteristics . Generator Protection – Setting Calculations Generator Protection Sample Relay Setting Calculations The sample calculations shown here illustrate steps involved in calculating the relay settings for generator protection. Line Distance. Current setting is the setting of current(pick-up current) in a relay at which we want to operate that relay. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and under-frequency. Electrical tools (MS Excel Spreadsheets) This section is dedicated to tools every electrical engineer can use in daily work.These spreadsheets below will make your job much more easier, alowing you to shorten the time used for endless calculations of cables, voltage drop, various selections of circuit breakers, capacitors, cable size and so on. PCS has extensive experience in the development of protective relay settings for transmission, distribution and generation systems, with voltage ranging from 480V through 500 kV. Fault MVA= 100 MVA/0.693=145 MVA=150 MVA (approx) 3 phase fault current at 6 kV bus=150/1.732*6 =14 KA. Hence, pick up electric current of the relay is, 1 × 150 % = 1.5 A Relay tripping time calculation according to IEC 60255 and IEEE. website. Relay Details Transformer Vector Group and CT to Relay Connection. The actual accuracy of the instrument transformers and relay Thermal Overload Relay setting = 120%x Full Load Current(Phase) Max. In order to make these calculations, knowledge of peak- Let's work through another sample calculation where the electric utility fault power level is known (click here to see Fig. Suppose we have connected on protection CT of ratio 200/1 A and electric current setting is 150%. Setting calculation is separated for overcurrent and eart fault relay with input parameters: Name of Feeder, Load Current: (IL) in Amps, Min Fault ABB RET670 Calculations. three phase current simple calculation. 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. The current settings of IDMTL relays are generally expressed in terms of plug setting. SEL787 and SEL 387/587 Transformer differential relay is used for this discussion. We will start the transformer differential protection calculation with the identification of … (Ps) for the older relays or Iset for the newes relays. Other methodologies and techniques may be … Min. Transformer Differential Protection Scheme works by using two separate quantities calculated from the primary current (IW1C) and secondary current (IW2C). Reply. relay setting calculation example overload relay setting and calculation electrical. ABB RED670 Fault Locator Calculations. Differential Relays 2. Plug Setting Multiplier of Relay. For 90 % of load CT output will be = 2.1 Amps, Set 2.1 amps as current limit in relay. Relay Settings Calculations / Helpful Excel Spreadsheets for Protection Engineers. Thermal Overload Relay setting = 70%x12.28 = 8.6A Max. pick up current current setting plug setting. Relay setting Calculation. Transformer Differential Protection Setting Calculation . Reply. 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 model setting calculations for typical ieds line. For a CT of 100/5A, if the relay is set to operate at 50A, Is will be set as 50A. Transformer Data : 8 MVA , 6.6KV/ 415 , Impedance = 0.0835 p.u., Tap + 10% ( 440Kv – 360KV. The basic formula for calculating the base resistor of the transistor is given by the expression: R = (Us - 0.6)hFE / Relay Coil Current, Where R = base resistor of the transistor, Us = Source or the trigger voltage to the base resistor, hFE = … With the proper education, tools, and references such as company standards available, a Base MVA=100 Fault MVA=1200 Source impedance=0.083 Cable impedance=.015*4=0.06 ohm Transformer impedance=11 % at 20 MVA base =0.11*100/20=0.55 ohm Total fault impedance at 6 kV Bus=0.083+.06+.55=0.693 ohm. If one wants to select an ovverload relay to trip off a three phase electric motor with a rated current of 15amps,what formula is to be used.Klockner Moeller states that the rated current is to be multiplied by 0.58..if that's true what's the formula. IDMT Curves; Transformer Differential. Outgoing Feeders setting… Generator ProtectionGenerator Protection Relay Setting Calculations 2. 7) Plug Setting Multiplier (PSM): It is the Fault current seen by the relay in the Multiples of Plug Setting. Kiran. The block diagram of the inverse-time overcurrent relay is shown in the figure. Step 4: Now we can find the fault current using the following formula: Fault current = net fault power ÷ (secondary XFMR voltage rating x √3) = 8,759kVA ÷ (12kV x √3) = 421A. electrical page 2 brian lambert. In order relays, the plug setting are in discrete steps starting 50% to 200% of the nominal rating of the overcurrent. Here I am assuming fault current in terms of CT secondary to be 6 A i.e. bitcoin core version 0 10 0 released. Protection Engineer. Generator protection calculations settings 1. UNIT CT VALUE A T60 Percent Differential element per unit value refers to setting scaled to the identified Unit CT. Thermal Overload Relay setting = 120%x12.28 = 14.7A. Calculation Formula. ABB Differential Relay Setting Calculation - Free download as PDF File (.pdf), Text File (.txt) or read online for free. In protective relay-based systems, the instantaneous overcurrent protection function is designated by the ANSI/IEEE number code 50. CTR = 800 /1. Earth fault relay an overview restricted earth fault protection 64r restricted earth fault relay relay settings calculations overcur protection for phase and Over Cur Earth Fault Relays 50 51 NumericalOver Cur Earth Fault Relays 50 51 NumericalSetting The Generator Protective Relay Functions EepPick Up Cur Setting Plug Multiplier AndSetting The Generator Protective Relay Functions EepRelay… Hence, Overload must be chosen closer to the range of 8.6-14.7. MiCOM P643 Calculations. Note : The CT operated thermal over load relay operates according to the the load current setting in the relay. These relays offer flexibility, self-checking, and ease of installation and often can provide additional functions over traditional electromechanical relays. Thermal Overload Relay setting = 70%x Full Load Current(Phase) Min. Over current/Earth fault Relays-Time Characteristics (51): Application Example on Transformer Differential Protection Calculation 25/33MVA 69/23kV Delta-Wye Transformer on SEL-387A Relay Figure 1. According to NEC,the general requirement for overload sizing be set around 115% or 125% from full load ampere.We should setting the overload relay within this parameter to avoid electric motor from serious damage. REF relay setting calculation REF RELAY SETTING CALCULATION. 2400 A in terms of primary and relay setting equal to 1 A in terms of secondary i.e. Protection Scheme works by using two separate quantities calculated from the primary (. 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