Multi-input distance relayMulti-input distance relay

By: Nikhil Kushwaha10M212

OutlineOutlineIntroductionPrincipleConic section charactersticsQuadrilateral charactersticsSweivelling charactersticsConclusionRefrences

IntroductionIntroductionWhen the inputs are raised to more

than two, then they are termed as multi-input comparators and they could be either amplitude or phase comparator or a combination of two.

With multiple-inputs duality between the comparators no longer exists.

They give non-classical characterstics.

PrinciplePrincipleIn recent years, greater attention has

been paid to distance relaying techniques of transmission lines. The main target of these techniques is to calculate the impedance the fundamental frequency between the relay and fault point. According to the calculated impedance, the fault is identified as internal or external to the protection zone. This impedance is calculated from the measured voltage and current signals at the relay location.

Conic section Conic section charactersticscharactersticsEllipseParabolaHyperbolaLimacon

Elliptical CharactersticsElliptical Characterstics

Parabolic characterstics :Such a characterstic can be used as blinder, i.e. To limit the area of another relay on R-X diagram

Hyperbolic characterstics :Can be realized using multi-input comparator. For the operation following condition should be satisfied:|Z-Zr|-|Z-KZr| < |Zr+KZr|

LimaconCharacterstics :They are use as blinders.ILZR [Kcos(ϕ-θ)-1]= VL

Multilateral or Multilateral or QuadrilateralQuadrilateral

Theoritically the ideal characterstics for distance relays would be a quadrilateral characterstics coincident with fault area.

Realisation of Quadrilateral Characterstics

Various characterstics resulting from the phase comparison of inputs indicated in the previous figure

θ

INTERPHASE SWITCHINGINTERPHASE SWITCHING

SWIVELLING SWIVELLING CHARACTERSTICSCHARACTERSTICSReactance relay is suitable for short lines.MHO relay is for long Tx lines. It will be better if a relay changes its

characteristics when line impedance ZL changes.

A circular relay characteristic is desirable for low ZS/ZL & straight line characteristic for high ZS/ZL.

To realize such characteristics, a fully cross-polarized MHO relay is used.

Such a relay operates reliably when a close-up fault occurs.

ZS/ZL = ∞

ZS/ZL = 0

ZS/ZL = 1

SWIVELLING CHARACTERSTICS

CONCLUSIONCONCLUSIONApplication of multiple input

comparators till now has been found in the field of distance relays.

Relays control output circuits of a much higher power.

Safety is increasedProtective relays are essential for

keeping faults in the system isolated and keep equipment from being damaged.

REFRENCESREFRENCES1. Power System Protection Static Relays : T S MADHAVA RAO.

2. Power System Protection and Switchgear : BADRI RAM & D N VISHWAKARMA.

3. Shrivastava, Kiran and Vishwakarma, D. N.(2007) 'Microcontroller-Based Numerical Quadrilateral Relay for the Transmission Line Protection', Electric Power Components and Systems.