gfcalc user guide (add-on edition).pdf

GFCalc (Ground Fault Current Calculation Program)

User Guide

Version 1.0

(e-DPP Add-On Edition)

ELTECHS Engineering & Consulting

March 2008

Copyright © 2006-2008

ELTECHS Engineering & Consulting Co., Ltd. All Rights Reserved

This manual has copyrights by ELTECHS Engineering & Consulting Co., Ltd. All rights reserved. Under the copyright laws, this manual may not be copied, in whole or in part, without the written consent of ELTECHS Engineering & Consulting Co., Ltd. The Licensee may copy portions of this documentation only for the exclusive use of Licensee. Any reproduction shall include the copyright notice. This exception does not allow copies to be made for other persons or entities, whether or not sold. Under this law, copying includes translating into another language. Certain names and/or logos used in this document may constitute trademarks, service marks or trade names of ELTECHS Engineering & Consulting Co., Ltd.or other entities.

Microsoft Access, Microsoft Excel, Windows 2000, Windows XP and Microsoft Word are registered trademarks of Microsoft Corporation.

ETAP and ETAP Power Simulator are registered trademark of Operation Technology, Inc. e-DPP is a registered trademark of ELTECHS Engineering & Consulting Co., Ltd.

ELTECHS Engineering & Consulting Co., Ltd. believes that the information contained herein is accurate as of its publication date, and such information is subject to change without notice. This information is provided "as is" without warranty of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose, or non-infringement. ELTECHS Engineering & Consulting Co., Ltd. assumes no responsibility for errors or omissions in this publication or any other documents referenced in this publication.

ELTECHS Engineering & Consulting Co., Ltd.

4-5-16 Narashinodai, Funabashi-shi, Chiba

User Guide Contents

Contents

Chapter 1 Preface........................................................................................................................ 1 1.1 Purpose of Program ..........................................................................................................1-1 1.2 Relation with e-DPP..........................................................................................................1-2 Chapter 2 System Model and Calculation Formula .............................................................2-1 2.1 Nomenclature ....................................................................................................................2-1 2.2 Non-Grounding System ....................................................................................................2-2 2.3 GTR – CLR System ..........................................................................................................2-7 2.4 NGR System.......................................................................................................................2-8 Chapter 3 Program Operation................................................................................................3-1 3.1 Getting Started and Basic Operation of Program .........................................................3-1 3.2 ｢Grounding Method｣ Page...............................................................................................3-5 3.3 ｢Ground Capacity｣ Page ..................................................................................................3-9 3.4 ｢Calculation｣ Page ..........................................................................................................3-12 3.5 ｢Protective Device｣ Page ................................................................................................3-15

Eltechs Engineering & Consulting i Ground Fault Current Calculation Program 1.0 (e-DPP Add-On Edition)

User Guide Preface

Chapter 1 Preface

<Abbreviations used in this user guide> Abbreviation Description

GTR Grounding Transformer EVT = (GPT)

Earthed Voltage Transformer = (Grounding Potential Transformer)

NGR Neutral Grounding Resistor CLR Current Limit Resistor DT Distribution Transformer OVG Ground Over Voltage Relay OCG Ground Over Current Relay DGR Directional Ground Over Current Relay

1.1 Purpose of Program

The ground fault current calculation program "GFCalc" calculates line-to-ground bolted fault currents in the following 4 standard grounding methods usually applied to a high voltage distribution system:

(1) Non-grounding (2) Grounding Transformer (GTR) – Current Limit Resistor (3) Grounding Transformer (GTR) – Neutral Grounding Resistor at Primary Winding (4) Distribution Transformer (DT) － Neutral Grounding Resistor

The objects and characteristics for impedance calculation are as follows:

• Current Limit Resistor (CLR) of Earthed Voltage Transformer (EVT) • Current Limit Resistor (CLR) of Grounding Transformer (GTR) • Neutral Grounding Resistor (NGR) of Grounding Transformer (GTR) • Neutral Grounding Resistor (NGR) of Distribution Transformer (DT) • Ground Capacity of Electrical Circuit C [micro F]

The way of handling these impedances varies upon an applicable grounding method as follows:

Grounding Method EVT - CLR GTR - CLR GTR - NGR DT - NGR C [micro F]

(1) Non-grounding (2) GTR -CLR (3) GTR - NGR (4) DT - NGR

Required Optional (blank) Not required GFCalc also performs the calculation of detective sensitivity (ground fault resistance) of OVG, OCG and DGR relays in addition to the calculation of line-to-ground bolted fault current.

Eltechs Engineering & Consulting 1-1 Ground Fault Current Calculation Program 1.0 (e-DPP Add-On Edition)

User Guide Preface

1.2 Relation with e-DPP The add-on edition of GFCalc (Ground Fault Current Calculation) program refers to e-DPP (electrical Data Processing Program) project and library. Particularly, Cable Schedule and Cable Library are referred by GFCalc since it draws the cable data from these entities. Therefore, prior to executing GFCalc, cable data shall be set up first in the menu "Edit" → "Cable" → "Cable Schedule". The following data is necessary as they are the ones being retrieved by GFCalc;

• Cable ID (Feeder name) • Rated voltage • Type (Insulation, jacket, etc.) • Size • Number of cores • Length • Connected switchboard ID • Connected bus ID

In general, the cable data in the Cable Schedule links with the library (cable) unless the said cable data was defined manually (not with the use of the library). When GFCalc is executed, GFCalc retrieves the cable data from e-DPP project and it interacts with the library to retrieves the associated capacitive admittance Y [Siemens] of the cables and at the same time converts them internally to capacitance [micro Farad]. (Note: e-DPP standard library contains Y data for JIS standard cables only.) GFCalc stores the data required for ground fault current calculation in the associated e-DPP project.

Eltechs Engineering & Consulting 1-2 Ground Fault Current Calculation Program 1.0 (e-DPP Add-On Edition)

User Guide System Model and Calculation Formula

Chapter 2 System Model and Calculation Formula 2.1 Nomenclature

f ： System frequency [Hz]

nC ： Ground capacity of the n-th feeder per phase [micro F] C ： Ground capacity of the entire HV circuit per phase [micro F]

aE ： Line-to-Ground voltage [V]

0V ： Zero sequence voltage [V] (By symmetric coordinates method)

0I ： Zero sequence current [A] (By symmetric coordinates method)

gI ： Line-to-Ground fault current [A] 03II g =

gR ： Fault resistance [ohm]

NR ： Neutral grounding resistance of DT or GTR [ohm]

1nR ： Resistance converted from GTR – CLR （） to NGR [ohm] 1eR

2nR ： Resistance converted from EVT – CLR （） to NGR [ohm] 2eR

1n ： Turn ratio of GTR

2n ： Turn ratio of EVT

0r ： Parallel resistance of zero sequence impedance

Cx ： Parallel reactance of zero sequence impedance

0Z& ： Zero sequence impedance (Resistance and capacitive reactance) CjXRZ −= 00&

Eltechs Engineering & Consulting 2 - 1 Ground Fault Current Calculation Program 1.0 (e-DPP Add-On Edition)


2.2 Non-Grounding System

(1) Calculation of Zero sequence impedance

The equivalent zero sequence resistance of EVT-CLR is;

)(3

3 22

22 Ω⋅= n

RR e

n (1-1)

If there are more than one EVT servicing in a system, the parallel combination of the equivalent zero sequence resistance of each EVT-CLR is taken. (Note: Zero sequence resistance is equal to 3 times of neutral resistance.) The zero sequence resistance is;

)(3 20 Ω= nRr (1-2)



The zero sequence reactance is;

)(2

11Ω

××==

CfCxC πω

(1-3)

Zero sequence impedance is composed of the parallel combination of zero sequence resistance (ro) and zero sequence reactance (xc) and is given by;

)(11

122

0

20

20

0

0

0

00 Ω+

⋅−⋅=

−⋅−

=

−+

=−=C

CC

C

C

C

C xrxjrxr

jxrrjx

jxr

jXRZ& (1-4)

The absolute value of zero sequence impedance is;

)(2200 Ω+= CXRZ& (1-5)

(2) Calculation of Line-to-Ground Bolted Fault Current As fault resistance in case of bolted faults, the zero sequence current is; 0=gR

)(210

0 AZZZ

EI a

&&&&

++= (1-6)

where;

21 , ZZ ≪ 0Z Then, approximately the line-to-ground bolted fault current is;

)(3

30

0 AZE

II ag &

&& == (1-7)

or



)(33

0

AxE

jrE

IC

aag +=& (1-8)

(3) Calculation of Detective Sensitivity for Ground Overvoltage Relay (64V) Provided the tertiary voltage of EVT is (V), and the setting value of the ground Overvoltage relay is (V), the relay operating condition is given as;

EV

SV

aEV0&≧

E

S

VV

(1-9)

where;

gag

a

a

g

aa RZZ

EZ

RZE

EZI

EIZ

EV

333 0

00

0

0000

+=×

+=×==

&

&&

&

&&&&& (1-10)

Then;

gRZ

Z

30

0

+&

&≧

E

S

VV

(1-11)

the fault resistance to meet the above criteria is given as; gR

gR ≦

( ))(

3

02

222

0

Ω

−−⎟⎟⎠

⎞⎜⎜⎝

⎛⋅+ RX

VVXR C

S

EC

(1-12)

Also, the line-to-ground fault current at the time of relay operation is calculated as;

( ))(

3

33

322

00

AXRR

ERZ

EI

Cg

a

g

ag

++=

+=

&& (1-13)

(4) Calculation of Detective Sensitivity for Ground Directional Relay (67G) As GFCalc applies the simplified method to the calculation of detective sensitivity of DGR, effect of the phase angle of maximum sensitivity of relay is ignored. <Voltage Element> Provided the setting of voltage element is (%), the operating criterion of relay is given by the formula similar to (1-11);

SV%



gRZ

Z

30

0

+&

&≧

100% SV

(1-14)

The fault resistance at which voltage input becomes equal or greater than (%) is given as; gR SV%

gR ≦

( ))(

3%100

02

222

0

Ω

−−⎟⎟⎠

⎞⎜⎜⎝

⎛⋅+ RX

VXR C

SC

(1-15)

Also, the line-to-ground fault current at the time of relay operation is calculated as same as the formula in (1-13). <Current Element> Since charged current derived from ground capacity of the faulted feeder does not flow through ZCT of the said feeder, the effective ground capacity at the location of fault is;

kCCC −=" [micro F] (1-16) Where; = Effective ground capacity at the location of fault "C = Total ground capacity of the grounding system under consideration C = Ground capacity of the faulted feeder kC Then recalculating zero sequence impedance using is; "C

""0

"0 CjXRZ −=& (1-17)

and the operating criterion of relay against the setting value (A) of current element is given as; SI

( ) 2"2"0

"0 3

33

3

Cg

a

g

a

XRR

ERZ

E

++=

+&≧ (A) (1-18) SI

The fault resistance at which current input becomes equal or greater than (A) is given as; gR SI

gR ≦ )(3

3 "0

2"2

Ω

−−⎟⎟⎠

⎞⎜⎜⎝

⎛RX

IE

CS

a

(1-19)

Also, the line-to-ground fault current at the time of relay operation is calculated as same as the formula in (1-13).



The smallest value out of these 2 fault resistances [(1-15) & (1-19)] calculated above will be an overall detective sensitivity of ground directional relay.

(5) Calculation of Detective Sensitivity for Ground Overcurrent Relay (51G) The calculation formulas in "(4) Calculation of Detective Sensitivity for Ground Directional Relay (67G) - <Current Element>" are applied for this device.



2.3 GTR – CLR System

In GTR - CLR grounding system, the zero sequence resistance of GTR - CLR is combined in the above "2.2 Non-Grounding System" in parallel. However, it is optional whether EVT is included or not. In case EVT is not included, the resultant zero sequence resistance consists of GTR -CLR resistance only. The equivalent zero sequence resistance of GTR-CLR is

)(3

3 21

11 Ω⋅= n

RR e

n (2-1)

If there are more than one GTR in service in a system, the parallel combination of the equivalent zero sequence resistance of each GTR is taken. Parallel calculation of the zero sequence resistances derived from the formulas (1-1) and (2-1) is as follow;

)(3

3 22

22 Ω⋅= n

RR e

n (1-1)

)(

31

31

1

21

0 Ω+

=

nn RR

r (2-2)

The same formulas as (1-3) through (1-19) in "2.2 Non-Grounding System" are applied to the calculation hereafter.



2.4 NGR System

The neutral grounding resistor is a method to connect a resistor to the neutral point of the secondary side of distribution transformer or the primary side of GTR. The same formulas are applied to both methods.



Zero sequence resistance of neutral grounding resistor is;

)(3 ΩNR (3-1) If there are more than one distribution transformers or GTRs of which the neutral points are grounded with resistor, the parallel combination of such are taken. Parallel calculation of the zero sequence resistances derived from the formulas (1-1) and (3-1) is as follow;

)(3

3 22

22 Ω⋅= n

RR e

n (1-1)

)(

31

31

1

2

0 Ω+

=

nN RR

r (3-2)

In case EVT is not included, the resultant zero sequence resistance consists of NGR resistance only.

)(30 Ω= NRr (3-3) The same formulas as (1-3) through (1-19) in "2.2 Non-Grounding System" are applied to the calculation hereafter.


User Guide Program Operation

Chapter 3 Program Operation 3.1 Getting Started and Basic Operation of Program

Getting the program started, select the e-DPP menu "Tools" → "Ground Fault Calculation...".

After "Ground Fault Current Calculation" dialog is brought up, click "Study Case" button to open a new dialog.



Select or copy the existing study case, or create a new study case you are going to examine on this dialog.

"Study case" is an entity where the set of input data used for the ground fault calculation is stored. Multiple study cases can be created. [Create] Create a new study case. Enter a new ID in "New Study Case ID" cell up to 26 characters and then click [Create] button. Any description up to 120 characters may be entered in "Description" cell. This is optional. [Copy] Create a new study case by copying the existing one. Select the source study case in "GFC Study Case ID" list, enter a new ID in "New Study Case ID" cell up to 26 characters and then click [Copy] button. "Description" cell is optional. Clicking the small [Copy] button adjacent to "Description" cell of the selected study case copies the content of existing "Description" cell to new one. Also, clicking the small [Save] button saves the content of "Description" cell. The existing "Description" cell is editable. [Delete] Delete the selected study case. If the currently loaded study case is deleted, the main screen of GFCalc will be reset. The study case once deleted cannot be restored.



[Select] Load the selected study case into the main screen of GFCalc. If another study case had been loaded before, all of screen data will be overwritten. [Help] Open the online help. [Close] Close the "Study Case" selection dialog. After the study case has been loaded, the main screen will populated with data (if any) as shown below.

There are six (6) pages (2 for future) in the dialog window. The six (6) buttons in the lower part are common to all the pages. [Calculate All] Perform the calculations in "Calculation" and "Protective Device" (described later) pages simultaneously in sequence. [Save All] Save all the active data in the four (4) pages. [To Excel] Export the input data and calculation results to MS Excel. It is necessary to confirm if the calculations had been completed using the latest data before exporting to MS Excel. Note that unless



the calculations are performed after the input data have been altered, there might be conflicts between the input data and the contents of MS Excel output report. [Study Case] Open "Study Case" selection dialog to switch to another study case. [Help] Open the online help. [Close] Close the main screen and terminate the ground fault current calculation program GFCalc.



3.2 ｢Grounding Method｣ Page

[Grounding Method] Select an applicable grounding method from the four (4) options.

According to the selected method, active data areas vary. [Distribution Transformer] Enter the rating of distribution transformers.

Irrespective of the selected grounding method, at least one distribution transformer needs to be specified. If there is the second or third transformer in parallel, check the checkbox "No.2" or "No.3" respectively and enter the appropriate data. Enter the line-to-line voltage of the transformer's primary and secondary winding in the "Prim. Voltage" and "Sec. Voltage" cells respectively. The secondary voltage is the one accounted in the system calculation. Note that the secondary voltage is assumed equal to all the transformers involved on the basis of parallelism, hence the same cells in the second and third transformers bear the same value entered in No.1. As "Capacity" and "Prim. Voltage" cells are not referred by the calculation, they are optional. [Earthed Voltage Transformer] Enter the rated voltage and the resistance value of current limit resistor of EVT.

When "Non-Grounding" method is selected, at least one set of EVT has to be specified. When the other method is selected, this data input is optional. Max. 8 sets of EVT can be specified. When two (2) or more EVT are specified, check the corresponding checkbox captioned "No.2" through "No.8".



Enter the line-to-line voltage in "Prim. Voltage" & "Sec. Voltage" cells and the induced voltage at a broken delta terminal in "Ter. Voltage" cells. These values are internally converted to the line-to-ground voltages by the program. The data entry in "Prim. Voltage" cell is valid for the first EVT only. The same cells of the second through eighth EVTs will have the same value as that of the first one and not editable. As "Sec. Voltage" cells are not referred by the calculation, they are optional. [Grounding Transformer (GTR)] - Current Limit Resistor (CLR) Method Enter capacity, rated voltage and resistance value of current limit resistor of GTR.

When "GTR - Current Limit Resistor" method is selected at least one set of GTR has to be specified. If there is a second or third GTR, check the checkbox "No.2" or "No.3" respectively and enter the appropriate data. Enter the line-to-line voltage in "Prim. Voltage" cells and the induced voltage at a broken delta terminal in "Sec. Voltage" cells. These values are internally converted to the line-to-ground voltages by the program. The data entry in "Prim. Voltage" cell is valid for the first GTR only. The same cells of the second and third GTRs will have the same value as that of the first one and not editable. As "Capacity" cells are not referred by the calculation, they are optional.



[Grounding Transformer (GTR)] - Neutral Resistor Method Enter capacity, rated voltage and grounding current or grounding resistance value of GTR.

When "GTR - Neutral Resistor" method is selected, at least one set of GTR has to be specified. If there is the second or third GTR, check the checkbox "No.2" or "No.3" respectively and enter the appropriate data. Enter the line-to-line voltage in "Prim. Voltage" cells and the induced voltage at a broken delta terminal in "Sec. Voltage" cells. These values are internally converted to the line-to-ground voltages by the program. The data entry in "Prim. Voltage" cell is valid for the first GTR only. The same cells of the second and third GTRs will have the same value as that of the first one and not editable. When "Current" or "Resistance" is entered, the other one is automatically calculated based on the primary voltage. As "Capacity" cells are not referred by the calculation, they are optional. [DT - Neutral Grounding Resistor] Enter the rated current or resistance of the NGR connected to the distribution transformers.

With "DT - Neutral Grounding Resistor" method is selected, at least one set of NGR has to be specified. When "Current" or "Resistance" is entered, the other one is automatically calculated based on the line-to-ground voltage "L-G Volt.". [Enlarge] button Enlarge the presently shown system image. Double clicking on the image will do the same operation.



[Save] button Save the data shown on the current page only. If all the data included in the other pages need to be saved as well, click [Save All] button instead.



3.3 ｢Ground Capacity｣ Page

This page lists the feeder cable data retrieved from e-DPP project and library databases. The gray cells are read-only while the white cells are editable.

[Read Data]

Read out the data from e-DPP cable schedule. The cables can be filtered with three (3) criteria namely "Cable Voltage", "Switchboard" and "Bus". Each criterion interacts with AND relationship. Specifying the criteria and then clicking [Read Data] button, the data will be loaded into the table. <Description of Table Columns>

[Select] Check the cables involved in the calculation. Summations of ground capacities and charged currents of the checked cables only are indicated in "Total" frame underneath the table. [Fault] Check the cable assumed to be ground faulted in the calculation. Only one cable can be checked. The charged current of the faulted cable does not flow through ZCT of the faulted feeder (Refer to Chapter 2.2, Formula (1-16)).



[Cable Data]

[Cable ID] [Type] [Core] [Size (mm2)] These data are retrieved from e-DPP cable schedule and not editable by user. If these data need to be modified, go to the cable schedule editor of e-DPP. [Length (m)] Length data are retrieved from e-DPP cable schedule as well. They are editable by user for case studies but the changes made here are not reflected to the e-DPP cable schedule. [micro F/1000m] Ground capacity C [micro F] of the associated cable derived from the admittance Y [S] data stored in e-DPP cable library per linear length.

[Ground Capacity (micro F)]

[Cable] Absolute Ground capacity C [micro F] of the associated cable. 【C-R】 If a feeder circuit breaker is of vacuum type and C-R suppressor is installed for the purpose of protection against switching surge, enter its ground capacity if any. Typical value is approx. 0.1 [micro F] per phase. [Motor] If ground capacity of a high voltage & large motor is not negligible, enter its capacity per phase. For reference, the typical values of ground capacity for high voltage, 3-phase, squirrel cage induction motors are shown below.

Ground Capacity of Several Types of High Voltage, 3-Phase, Squirrel Cage Induction Motors (Reference Data) 3300V 60Hz Machine micro F/phase

110kW 160kW 300kW 2P 4P 6P 2P 4P 6P 2P 4P 6P

0.019 0.022 0.034 0.024 0.029 0.038 0.034 0.039 0.052

500kW 850kW 1000kW 2P 4P 6P 2P 4P 6P 2P 4P 6P

0.053 0.055 0.075 0.063 0.075 0.093 0.045 0.11 0.12

1500kW 2P 4P 6P

0.048 0.16 0.17 [Others] If there are other devices for which the ground capacity needs to be considered, enter their values. [Total]

Summation of ground capacity of the above [Cable], [C-R], [Motor] and [Others].



[Charged Current (A)] Charged current due to the total ground capacity of each feeder If the number of a certain feeder is m and its ground capacity per phase is , the charged current is calculated as;

mC

mI

)(6 AECfI amm ⋅⋅= π <Descriptions of Other Buttons> [Calculate] button Recalculate the charged currents (A) in the table. [Save] button Save the data shown in this page only. If all the data included in the other pages need to be saved as well, click [Save All] button instead. [Preview] button Click "Preview" button to show printable layout of the ground capacity table (grid). [To Excel] button Export the data in the table to MS Excel. [Selected Only] / [Show All (E)] button Toggle to show the checked records only or show all records instead.



3.4 ｢Calculation｣ Page

According to the formulas described in Chapter 2 and the input data in the "Grounding Method" & "Grounding Capacity" pages, the zero sequence impedance and ground fault current at a line-to-ground bolted fault are calculated in this page.

If "0 (ohm)" is shown in the resistance, reactance or impedance cell, it means such device or element is not present (ironically it means "Infinite" (ohm)). Note that it does not mean the circuit is shorted. [Calculate] button Perform a calculation on the current page only.



[Zero Sequence Resistance (ohm)] Equivalent zero sequence resistances derived from grounding characteristics of each devices. "Composite Resistance ro" is the total resistance of the parallel combination of all the zero sequence resistances involved.

[Zero Sequence Reactance (ohm) <For L-G Bolted Fault Current Calculation>] Total zero sequence reactance due to the total ground capacity of the entire grounding system under consideration.

[Zero Sequence Impedance <For L-G Bolted Fault Current Calculation>] Total zero sequence impedance due to the parallel combination of "Composite Resistance ro" and "Composite Reactance xc". "Ro-jXc" is the equivalent series model of the parallel combination of "Composite Resistance ro" and "Composite Reactance xc"



[Zero Sequence Reactance (ohm) <For ZCT Through Current Calculation>] The net zero sequence reactance at the location of the faulted feeder. Refer to "(4) Calculation of Detective Sensitivity for Ground Directional Relay (67G) <Current Element" for related information.

[Zero Sequence Impedance <For ZCT Through Current Calculation>] The net zero sequence impedance due to the parallel combination of "Composite Resistance ro" and "Composite Reactance x"c at the location of the faulted feeder. "R"o-jX"c" is the equivalent series model of the parallel combination of "Composite Resistance ro" and "Composite Reactance x"c"

[L-G Bolted Fault Current Calculation (Rg=0)] This section indicates the calculated line-to-ground bolted fault due to [Zero Sequence Impedance <For L-G Bolted Fault Current Calculation>] above.

The designated system's grounding method is shown in white foreground.



3.5 ｢Protective Device｣ Page

According to the formula describe in Chapter 2, the detective sensitivities of the three (3) common types of relays, OVG, OCG, and DGR are calculated here including their pick-up current.

[Ground Overvoltage Relay (OVG - 64V)] Enter the rated zero sequence voltage and setting of OVG relay.

The setting value must be less than the rated zero sequence voltage.



[Ground Overcurrent Relay (OCG - 51G)] Enter the rated current and setting of OCG relay.

As "Rated Current" cell is not referred by the calculation, this input is optional. Note that if an improper value is entered in "Setting" cell, the detective sensitivity (fault resistance) might become negative (negative resistor). [Ground Directional Relay (DGR - 67G)] Enter the rated zero sequence voltage, rated current, their settings and phase angle of maximum sensitivity of DGR relay.

As "Rated Zero Sequence Voltage", "Rated Current" or "Phase Angle of Max Sensitivity" cell is not referred by the calculation, these inputs are optional. Note that if an improper value is entered in "Setting" cell for the current element, the detective sensitivity (fault resistance) might become negative (negative resistor). The lower value between the calculated two (2) fault resistances and the corresponding fault current is the one accounted in "Detective Sensitivity" - "Overall" cells. [Overall Detective Sensitivity - Fault Resistance] Overall detective sensitivities for the combination of OVG+OCG and OVG+DGR relays are indicated here. In each combination, the lower value of fault resistance between the two (2) relays is the one accounted.



[CT - Rated Current (A)】 Enter the rated current of each winding of CT.

As they are not referred by the calculation, these inputs are optional. [ZCT - Rated Current (A)】 Enter the rated current of each winding of ZCT.

As they are not referred by the calculation, these inputs are optional.

[Calculate] button Perform the calculation on the current page only. As the calculation in this page is based on the data in the "Calculation" page, it is necessary to execute the calculation in the "Calculation" page in prior. Note that if the data in the other pages were modified and the calculation in the "Calculation" page has not been performed yet there might be a conflict in the calculation results in this page. When the entire calculations are performed by [Calculate All] button located in the lower area, no conflict will occur.

[Save] button Save the data shown in this page only. If all the data included in the other pages need to be saved as well, click [Save All] button instead.

(End of Document)


gfcalc user guide (add-on edition).pdf

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