Com Trade Relay

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ECE 525:Power Systems Protection and Relaying

Session 23; /15Fall 2006

Simple Relay Model The MathCAD sheet below implements some basic relay calculations. The file takes data read from a Comtrade file

and postprocesses it.

The matrix "data" below is the data captured from a COMTRADE "*.dat" file. To read in a data file remove the table currently at the

top of the file. Then choose "Insert" ---> "Component".

This will open a dialog box. One option is to choose "Input Table".•

* Then select the first cell in the table and right click your mouse and choose "Import".* Then browse to the "*.dat" COMTRADE file and select. This will fill in the data in the table. Then name the variable as "data

Another option is to choose "File Read or Write".•

* This will open a dialog box, choose Text file

* Browse for file with extension .txt or .csv.

* Your assignments will tell you which files to open.

The example below uses the File Read or Write option.•

data

C:\..\loop5.dat

:=You may need to browse a bit to find this file when you open this sheet.





data

0 1 2 3 4 5 6

01

2

3

4

5

6

7

8

9

10

11

12

13

14

15

1 0 -1.538·104

-1.124·104

1.003·104

-8.402·103

-1.223·104

2 1.041·103 -3.17·104 -3.13·104 1.63·104 -5.523·103 -3.276·104

3 2.083·103 -1.859·104 -3.179·104 1.073·104 2.778·103 -2.883·104

4 3.125·103 -9.781·103 -3.191·104 7.028·103 8.181·103 -2.601·104

5 4.166·103 4.993·103 -2.432·104 1.018·103 1.233·104 -1.541·104

6 5.208·103 1.561·104 -1.522·104 -3.159·103 1.295·104 -5.027·103

7 6.25·103 2.648·104 -2.103·103 -7.348·103 1.119·104 8.471·103

8 7.291·103 3.105·104 9.855·103 -8.88·103 6.307·103 1.902·104

9 8.333·103 3.276·104 2.153·104 -9.249·103 -85 2.841·104

10 9.375·103 2.776·104 2.88·104 -6.892·103 -7.788·103 3.225·104

11 1.042·104 2·104 3.263·104 -3.509·103 -1.493·104 3.259·104

12 1.146·104 7.779·103 3.057·104 1.597·103 -2.106·104 2.702·104

13 1.25·104 -4.419·103 2.465·104 6.541·103 -2.466·104 1.851·104

14 1.354·104 -1.714·104 1.418·104 1.159·104 -2.573·104 6.415·103

15 1.458·104 -2.622·104 2.227·103 1.503·104 -2.359·104 -5.62·103

16 1.563·104 -3.235·104 -1.075·104 1.722·104 -1.905·104 -1.745·104

=

The COMTRADE file is actually three files. One has an extension "*.hdr". This file will be emtpy in this case. Another has the

extension "*.dat". This has the actual numerical data in columns of numbers. The third file is a configuration file and has the

extension "*.cfg" and this tells the program reading the numerical data what the columns represent. The configuration file provides

scaling and offset information for each of the variables stored as vectors. Here is a typical entry:

1,TACS LEM6IN,,,,2.6836E-06,7.6143E-04,0.0000E00,-32765,32765,1,1,P

Each data record starts entry number (1-7 here), the name for the measurements (for example "TACS LEM6IN").

The number after the 4 commas is a scale factor. Copy this number into value Irscale below (In is the same as the residual current

Ir). Do likewise with the voltage and current entries. The numbers listed above are the ones currently entered in the MathCAD file.





If RS 1− rows data( ) 1−..:=

vRS

4rows data( ) 1−..:=

i 0 rows data( ) 1−..:=

Enter vector indices for filter and relay calculations (do not change these)

RS 16:=a 1 e120j deg⋅

⋅:=

Enter Constants. Note that RS is the sampling rate, and the value of 16 here is assuming that the COMTRADE file was sampled at

that rate.

Ir

offset

7.6143 10-4

⋅:=Ir

scale

2.6836 10-6

⋅:=

Vcoffset 2.5105 10-1

⋅:=Vcscale 4.8099 10-3

⋅:=Icoffset 1.6207:=Icscale 2.5779 10-4

⋅:=

Vboffset 2.4410:=Vbscale 4.8154 10-3

⋅:=Iboffset 1.5161−:=Ibscale 3.7742 10-4

⋅:=

Vaoffset 5.3129−:=Vascale 4.8918 10-3⋅:=Iaoffset 3.1708 10-2⋅:=Iascale 1.5269 10-4⋅:=

Scaling and Offset Data from Comtrade CFG file.

The next number is an offset factor. If you use the MathCAD sheet, copy this number into the sheet as Ioffset (In is the same as the

residual current Ir). Do likewise with the voltage and current entries. The numbers listed above are the ones currently entered in theMathCAD file.

If you don't change the scaling and offset factors, the waveforms you evaluate won't be correct. The MathCAD sheet has further

instructions.





Read Data From Comtrade File:

The data from the COMTRADE file is now read into vectors for MathCAD to use.•

Note that these vectors are assuming that IA, IB, etc are in certain columns in the table. The numbers below assume that the•

data is assigned as described in the other handout. Columns 0 and 1 of the COMTRADE file do not store data, so Column 2

is the first one of interest.

Since the neutral current IN was measured, that will be used for the residual current (IR = 3I0).•

IRdata

2⟨ ⟩

CTR

Ir

scale⋅ Ir

offset+:=

VAdata

6⟨ ⟩

PTR

Vascale⋅ Vaoffset+:=

IAdata

3⟨ ⟩

CTR

Iascale⋅ Iaoffset+:=

VBdata

7⟨ ⟩

PTR

Vbscale⋅ Vboffset+:=

IBdata

4⟨ ⟩

CTR

Ibscale⋅ Iboffset+:=

VC

data8⟨ ⟩

PTR

Vcscale⋅

Vcoffset+:=

ICdata

5⟨ ⟩

CTR

Icscale⋅ Icoffset+:=





Now plot the currents and voltages. These should be sinusoidal. Note that the horizontal axis is in the number of cycles since the

i/RS is sample number divided by sampling rate.

0 2 4 6 8 10 1215

10

5

0

5

10

15

IAi

IBi

ICi

IRi

i

RS

Since the residual current stayed at 0 andthe currents in two phases increased, this

was probably a line-to-line fault.





0 2 4 6 8 10 12

200

100

0

100

200

VAi

VBi

VCi

i

RS

Digital Filter Stages:

Now the data is run through a digital cosine filter as a first step in calculating magnitude and phase. Normally the first step•

would be to perform a low pass filtering operation on the data, but since ATP Analyzer already did this, we can skip that step.

You will learn more about applications of digital filters for relays in ECE 526.•

Each of the measurements is filtered.•





IaIf

2

RS0

RS 1−

k

cos2 π⋅ k ⋅

RS

IAIf RS 1−( )−[ ] k +

⋅

∑=

⋅:=Va

If

2

RS0

RS 1−

k

cos2 π⋅ k ⋅

RS

VA

If RS 1−( )−[ ] k +

⋅

∑=⋅:=

IbIf

2

RS0

RS 1−

k

cos2 π⋅ k ⋅

RS

IBIf RS 1−( )−[ ] k +

⋅

∑

=

⋅:=Vb

If

2

RS0

RS 1−

k

cos2 π⋅ k ⋅

RS

VBIf RS 1−( )−[ ] k +

⋅

∑

=

⋅:=

IcIf

2RS

0

RS 1−

k

cos 2 π⋅ k ⋅RS

ICIf RS 1−( )−[ ] k +

⋅ ∑=

⋅:=

VcIf

2

RS0

RS 1−

k

cos2 π⋅ k ⋅

RS

VCIf RS 1−( )−[ ] k +

⋅

∑

=

⋅:=

IrIf

2

RS0

RS 1−

k

cos2 π⋅ k ⋅

RS

IRIf RS 1−( )−[ ] k +

⋅

∑

=

⋅:=

Now create phasors:

First map everything back to upper letters•

The calculate line to line voltages.•

VAB VA VB−:= VBC VB VC−:= VCA VC VA−:=





To create a phasor we need a real and an imaginary part. If one uses Euler's identity, we need: cos(A) + j sin(A). The cosine•

filter output gives us the cosine part. Rather than implementing a sine filter (which doesn't reject decaying DC offsets), create the

sine term by delaying the cosine terms by 00 degress (1/4 cycle-- or 4 samples when sampling at 16 samples per cycle).

VAcpxv

Vav

j Va

vRS

4−

⋅+:=IAcpx

vIa

v j Ia

vRS

4−

⋅+:= IRcpxv

Irv

j Ir

vRS

4−

⋅+:=

VBcpxv

Vbv

j Vb

vRS

4−

⋅+:=IBcpx

vIb

v j Ib

vRS

4−

⋅+:=

VCcpxv

Vcv

j Vc

vRS

4−

⋅+:=ICcpx

vIc

v j Ic

vRS

4−

⋅+:=

Each of these terms is a phasor with magnitude and phase.•

0 2 4 6 8 10 120

5

10

15

IAcpxv

IBcpxv

ICcpxv

IRcpxv

v

RS

0 2 4 6 8 10 120

40

80

120

160

200

VAcpxv

VBcpxv

VCcpxv

v

RS





0 2 4 6 8 10 1215

10

5

0

5

10

15

IBcpxv

IBi

v

RS

i

RS,

Notice that the DC offset does not

pass through the magnitude

calculation.

Create symmetrical components:

V0v

1

3

VAcpxv

VBcpxv

+ VCcpxv

+( )⋅:=

I0v

1

3 IAcpxv IBcpxv+

ICcpxv+

( )⋅:=

V1v

1

3VAcpx

va VBcpx

v⋅+ a

2VCcpx

v⋅+⋅:=

I1v

1

3IAcpx

va IBcpx

v⋅+ a

2ICcpx

v⋅+⋅:=

V2v

1

3VAcpx

va2

VBcpxv

⋅+ a VCcpxv

⋅+⋅:=I2

v

1

3IAcpx

va2

IBcpxv

⋅+ a ICcpxv

⋅+⋅:=





0 2 4 6 8 10 12

0

2

4

6

8

I0v

I1v

I2v

v

RS

0 2 4 6 8 10 120

50

100

150

200

V0v

V1v

V2v

v

RS





Relay Model:

1. Ground and negative sequence over current elements

A. First plot the negative and zero sequence currents and compare them to the settings. Note that the settings needs

an extra SQRT(2) factor since the digital filter is giving us the peak amplitude and not the RMS value.

0 50 100 150 2000

2

4

6

I2v

2

Level_1_50Q

Level_2_50Q

v

Note that the negative sequence current

crosses the level 2 threshold, so the relaywould issue a time delayed trip. Also note

that the start up transient in the relay almost

exceeded this threshold.





0 50 100 150 200

0

1

2

3

4

5

6

I0v

2

Level_1_50G

Level_2_50G

v

In this case the zero sequence current isnever very large

B. Simple relay logic expressions.

Level1Q_puv

1

I2v

2Level_1_50Q≥if

0 otherwise

:= Level2Q_puv

1

I2v

2Level_2_50Q≥if

0 otherwise

:=

Level1G_puv

1

I0v

2Level_1_50G≥if

0 otherwise

:= Level2G_puv

1

I0v

2Level_2_50G≥if

0 otherwise

:=

Note that these elements are not well done, and could "chatter" since they don't latch.





Instantaneous Overcurrent Element Outputs

0 50 100 150 2000

0.5

1

1.5

Level1Q_puv

Level2Q_puv

v

0 50 100 150 2000

0.5

1

1.5

Level1G_puv

Level2G_puv

v

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