Overview

Dear All,Trainer Introduction:Your trainer brings over 21 years of experience in operation & maintenance, erection, testing, project management, consultancy, supervision, substation automation, SCADA, and commissioning. With a background spanning power plants, high voltage substations, and HVDC installations, he has worked with renowned organizations such as Siemens Saudi Arabia. He has been involved in over 20 high-voltage substation projects across Pakistan and Saudi Arabia.His expertise encompasses a wide range of areas including protection systems, substation automation systems, design, testing, and commissioning of power generation systems, high voltage switchgear, protection relays, and control schemes. He has a proven track record of leading testing and commissioning teams for implementing electrical infrastructure projects for industrial clients, including steel and petrochemical industries.Protection Element Setting:Functional Scope:The SEL-787 has three differential elements (87R-1, 87R-2, and 87R-3).These elements employOperate (IOP) and Restraint (IRT) quantities that therelay calculates from the winding input currents.Figure shows the relay characteristic. You can set the characteristic as either a single-slope, percentage differential characteristic or as a dual-slope, variable-percentage differential characteristic. Tripping occurs if the Operate quantity is greater than the curve value for the particular restraint quantity.A minimum pick up level for the Operate quantity must also be satisfied.The four settings that define the characteristic are:O87P = minimum IOP level required for operationSLP1 = initial slope, beginning at the origin and intersecting O87P atIRT = O87P • 100/SLP1IRS1 = limit of IRT for SLP1 operation; intersection where SLP2 beginsSLP2 = second slope must be greater than or equal to SLP1The relay (SEL-787) use the transformer MVA rating as a common reference point, TAP scaling converts all secondary currents entering the relay from the two windings to per unit values, thus changing the ampere valuesinto dimensionless multiples of TAP. Throughout the text, the term "TAP" refers to the per-unit value common toboth windings. This method ensures that, for full-load through-current conditions, all incoming current multiples oftap sum to 1.0 and all outgoing current multiples of tap sum to -1.0, with a reference direction into the transformer windings.In this course, we will perform the setting calculation of 26MVA transformer with following data:Type of cooling: ONAN / ONAFVector Group: Dyn11Rated Voltage HV V: 132000Rated Voltage LV V: 12000Full Load current HV A: 87.48 / 113.72Full Load current LV A: 1004.12 / 1305.35Rated Power MVA: 20 / 26% impedance at normal tap (12 no.): 15.35% / 19.95 %Type of tap changer: On loadVoltage at maximum tap V: 151800Voltage at minimum tap V: 112200Further we will calculate: Protection Settings Calculations for Power TransformersFull load amperesShort circuit MVAShort circuit current at HV & LV sidesrelationship between short circuit MVA and percentage impedance of transformerMagnitude and phase angle error and its compensationCT error and its compensationOperating and restraining currentsPickup current calculationsTAPN calculationsPhase angle compensation settingsSlope 1 & 2 calculationsHarmonics blocking calculations.Best Regards

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