CJC FIBRECOMMUNICATIONS INFRASTRUCTURE Discuss Your Project
HOME / Calculation of Relay Protection Braking Coefficient

Calculation of Relay Protection Braking Coefficient

Fiber and communications infrastructure knowledge brief Published 04 Sep 2021

Use this reference to prepare product questions for CJC FIBRE. Check interfaces, capacity, protection and installation requirements against the current product documentation.

The relay protection braking coefficient is calculated as the ratio of the operating current of the upstream relay to the downstream relay, adjusted for time grading and relay characteristics to ensure selective coordination.

Definition and Purpose

The braking coefficient (also called the coordination factor) is used in overcurrent relay coordination to prevent upstream relays from tripping before downstream relays during a fault. It ensures selectivity, allowing only the relay closest to the fault to operate first while upstream relays act as backup protection.

Step-by-

Step Calculation

Determine Fault Currents Identify the short-circuit current at the relay locations. For downstream relays, calculate the maximum fault current they may experience. For upstream relays, consider the fault current at their location, which may include contributions from multiple feeders.

Set Pickup Currents Define the pickup current (I_pickup) for each relay. This is the minimum current at which the relay will operate. Typically, the downstream relay is set slightly above the maximum load current, while the upstream relay is set higher to avoid unnecessary tripping.

Calculate Time Dial Settings For inverse-time relays, the operating time depends on the fault current and the relay's time-current characteristic. The time dial (TDS) adjusts the relay's operating time. The upstream relay's operating time must be longer than the downstream relay's by a grading margin (t_margin), usually 0.

2–0. 3 seconds for numerical relays. Compute the Braking Coefficient The braking coefficient Kb is calculated using the formula: Kb=Ifault,upstream/Ipickup,upstreamIfault,downstream/Ipickup,downstream Where: Ifault,upstream = fault current at the upstream relayIpickup,upstream = pickup current of the upstream relayIfault,downstream = fault current at the downstream relayIpickup,downstream = pickup current of the downstream relay This ratio ensures that the upstream relay operates slower than the downstream relay for the same fault, maintaining selectivity.

Adjust for Relay Characteristics If the relays are extremely inverse or very inverse, the time-current characteristic constants must be considered. The operating time of the upstream relay is then: tupstream=tdownstream+tmargin The multiple of pickup current for the upstream relay can be recalculated using the relay's characteristic curve to match the desired operating time.

Practical Considerations

Ensure the CTs are not saturated at maximum fault current. Verify that the grading margin is sufficient to account for relay tolerances and breaker operating times. For numerical relays, software tools can automate the calculation of braking coefficients and time dial settings, but manual verification is recommended.

By following these steps, the relay protection braking coefficient can be accurately determined, ensuring reliable and selective operation of the protection system.

Calculation of Relay Protection Braking Coefficient - CJC FIBRE CONSULTANTS [PDF]

Calculation of Relay Protection Braking Coefficient

Relay Settings Calculations

Protection selectivity is partly considered in this report, and could be also revaluated. Names of parameters in this calculation may differ from those in appropriate device.

Efficient searching of extreme operating conditions for relay

This paper presents a novel deep reinforcement learning-based approach for the rapid identification of Extreme Operating Conditions (EOCs) in relay protection setting calculation.

CALCULATION AND SETTING OF RELAYS IN TRANSMISSION

The proposal itself and define the different protection zones should be based on impedance lines to be determined by the calculation referred to in the previous section of this article.

Protection Relay Setting Interactive Calculator | FIRGELLI

Use this Protection Relay Setting Calculator to calculate pickup current, time multiplier settings (TMS), operating time, coordination time interval (CTI), and plug setting multiplier (PSM)

Generator Relay Protection Setting Calculation | PDF

Generator relay protection setting calculation instruction Instruction: This setting calculation instruction is only for reference, protection device running setting is confirmed by user.

Relay Setting Calculation Overview | PDF | Volt | Relay

The document provides calculations for relay settings for different components in a power system network.

FEEDER PROTECTION CALCULATIONS & SETTINGS

Relay 8 backs up relays 6 and 7, and should be co-ordinated with the slowest of these two relays. Relay 7 has an instantaneous setting of 1100 A, which is smaller than the setting of relay 6, and so the

RELAY SETTING CALCULATION

To determine stability voltage for through fault Vs'' Voltage across the relay at IFS (VS) CT Resistance (RCT)

A Guide for Calculating Step Distance Relay Settings

For two-terminal or three-terminal lines where the remote station has a single-circuit breaker with breaker failure protection, set the relay to reach 125% of the Zone 2 relay reach.

FEEDER PROTECTION CALCULATIONS & SETTINGS

Protection Coordination Principles Relay coordination is the process of selecting settings that will assure that the relays will operate in a reliable and selective way. In OC relays the coordination is based on

Calculation of safe braking curves and vital relay redundancy in train

Safe Braking Curve Calculation The Safe Braking Curve (SBC) directly addresses your query regarding mathematical models in train protection. It calculates the guaranteed emergency

RELAY SETTING CALCULATION

Calculation for Transformer Differential Protection 87T settings : Rated Current @ 67 MVA at Highest tap= MVA*1000/SQRT(3) x KV 299 A Rated Current @ 67 MVA at Nominal tap=

POWER SYSTEM PROTECTION AND RELAY COORDINATION

Power System Protection philosophies Short-circuit calculations (Ohmic Methodology / Per Unit Calculation (IEC 60909/ IEEE 242 :1986)) Instrument Transformer (CT''s, PT''s) selection &

Fast calculation on branch coefficient in protection relay setting and

At present, general method to calculate branch coefficient needs fault calculation in different operation modes to get protective branch current and mating branch current. According to sequence current

Relay Time Calculation Formulas | True Geometry''s Blog

Explanation Relay Operating Time Calculation: This calculator estimates the operating time of an overcurrent relay based on common parameters. The formula for operating time is a

CALCULATION AND SETTING OF RELAYS IN TRANSMISSION

Abstract. This article deals with the issue of protective relays in terms of protecting high voltage lines. At the beginning of the article it is drawn up process to protect power lines. Consequently, it is shown

Protection Relay Settings Calculations Made Easy

Power System Protection Setting Calculations The electrical grid is a vast and intricate system designed to ensure the seamless flow of electricity from power generation facilities to end

Relay Protection in HV/MV Substations: Calculations, Settings

Effective relay protection in HV/MV substations requires a thorough approach encompassing calculations, precise settings, meticulous coordination, informed relay selection, and

Related Video Reference

This video was associated with the source search result. Verify technical details against current product documentation and project requirements.

Technical note

This reference is intended for preliminary fiber and communications infrastructure research. Optical interface, fiber type, port or core capacity, electrical input and output, enclosure protection, cooling, installation limits and applicable standards must be verified for the specific project.

Latest Fibre Network Insights

Still Have a Technical Question?

Use the inquiry form to describe the product category, application, interfaces, capacity and installation environment.

Start a Project Inquiry