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FUNCTION CHARACTERISTICS

103

One adjustable operation threshold, (U

E3H

<) with deﬁnite time adjustable delay (t

UE3H

<).

In order to avoid unwanted operation of protection to stop the generator or operating conditions

at low load conditions, where the third harmonic component is absent, the following controls are

provided:

• Generator stopped: the inhibition of protection can be obtained by activating a logic input. The set-

tings are available inside 100% stator earth-fault with 3rd harmonic - 27H-59H \ 1st Pickup Element

\ Setpoint menu; if the Block1 enabling parameters are set to ON and a binary input is designed for

logical block (Block1), the protection is blocked off whenever the given input is active.

The trip timer is held in reset condition, so the operate time counting starts when the input block

goes down.

[1]

The enabling parameters are available inside the Proﬁle A(or B) \ Undervoltage-27

\ 1st Pickup Element (2nd Pickup Element) \ Setpoints menus, while the Block1 function must be

assigned to the selected binary input inside the Common parameters \ Binary input allocation menu.

menus (IN1 or INx matching). In particular it is cleared the trop timer, so the operating time count

begins when the signal block goes OFF. Alternatively, inhibition can be obtained by programming an

undervoltage control. The 100% stator earth would then be inhibited when all three voltages measu-

red by the VTs fall below an adjustable threshold (U

IN-3H

<)). This requires the setting to ON of the the

State parameter of the U

IN-3H

< threshold.

• Generator at low load: inhibition of the protection can also be set when all three phase currents

are below an adjustable threshold (I

IN-3H

< ) in order to avoid the trip with generators with no third

harmonic voltage at reduced load. This requires the Status parameter set to ON on the I

IN-3H

<thre-

shold. This inhibition is off the intervention of the monitoring function of the CT. This requires the

setting to ON of the the State parameter of the U

IN-3H

< threshold. This inhibition is cleared when

the CT Supervision function (74CT) becomes active.

Measurement of residual voltage measured by VT secondary open delta on the generator line

The operating logic must be programmed as third harmonic overvoltage protection (59H) in order to

detect an increase in the value of third harmonic component of residual voltage (present in normal

operation), in the case of earth fault near the star center.

The development of the third harmonic residual voltage on the winding stator is shown in the fol-

lowing ﬁgure.

Note 1 The exhaustive treatment of the logical block (Block 1) function may be found in the “Logic Block” paragraph inside CONTROL AND MONITOR-

ING section.

E3H

UE3H

TRIP

General operation time characteristic curve for the third harmonic undervoltage element - 27H

E3H

IN-3H

E3H

UE3H mode

UE3H element

U< inhibition

Block1

Block3

UE3H Start

UE3H Trip

E3H

AND

27H-59H Element

Inhibit U<

, U

U < U

IN-3H

AND

Inhibit I<

, I

I < I

IN-3H

General logic diagram of the 3rd harmonic undervoltage/overvoltage element - 27H-59H

XMR-D EQUIPMENT MANUAL

Ed. 2.9 - 02/2021

Brand	Thytronic
Model	XMR-P 4l+4V
Category	Protection Device
Language	English

Thytronic XMR-P 4l+4V User Manual

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