ABB optical fiber conversion module NAIO-03F, new and original, one-year warranty inquiry

Description

NAIO-03F Since the transformer load is calculated using the maximum current from phases A, B, or C,

the displayed load should be:

where

(EQ 7.2)

 Verify the harmonic content display in A2 METERING  HARMONIC

CONTENT  THD  W1…W2…W3.

It should be zero or equal to distortion of input current.

 Verify frequency shown in A2 METERING  FREQUENCY 

SYSTEM FREQUENCY.

It should be 60 or 50 Hz, as per frequency NAIO-03F of input current on Phase A.

 To verify the positive and negative sequence component values, apply

the current signal to Phase A of each winding in series.

Read the values of positive and negative sequence current displayed by

the relay.

where a = 1∠120°

(EQ 7.3)

(EQ 7.4)

All angles will be 0°. These values are displayed in the A2 METERING  CURRENT 

POSITIVE SEQUENCE  W1…W2…W3 and A2 METERING  CURRENT  NEGATIVE

SEQUENCE  W1…W2…W3 actual values menus.

 Lower the current amplitude while displaying the system frequency.

 Verify that the frequency is displayed NAIO-03F correctly with current levels down

to approximately 50 mA RMS input.

 Decrease current to 0 A.

7.4.3 Voltage Input

 Connect an AC voltage to the voltage input (if the input voltage feature

is enabled) to terminals C11 and C12.

 Set the level at the expected VT secondary voltage on the VT for your

installation.

 Remove all current signals from the relay.

 Verify the voltage reading in A2 METERING  VOLTAGE  SYSTEM

LINE-TO-LINE VOLTAGE.

The reading should be equal to the input voltage × VT ratio.

Note

The displayed system voltage is always the line-to-line voltage regardless of the input

VT signal. Earlier versions of the 745 may display the same voltage as the selected

input, i.e. phase-to-neutral if NAIO-03F the input is a phase-to-neutral signal and phase-to

phase if the input is phase-to-phase.

 With the voltage signal still ON, read the displayed system frequency

under A2 METERING  FREQUENCY  SYSTEM FREQUENCY.

 Lower the voltage amplitude while displaying the system frequency.

 Verify that the frequency is displayed correctly with voltage levels down

to less than 3 V RMS input (when the lower limit is reached, the system

frequency will be displayed as 0.00 Hz).

 Verify that at less than 1.0 V, frequency is displayed as 0.00 Hz.

7.4.4 Transformer Type Selection

7.4.4.1 Description

The 745 automatically configures itself to correct for CT ratio mismatch, phase shift, etc.,

provided that the input CTs are all connected in wye. The following example illustrates the

automatic setting feature of the 745.

7.4.4.2 Automatic Transformation

The automatic configuration routines examine the CT ratios, the transformer voltage

ratios, the transformer phase shift, etc., and apply correction factors to match the current

signals under steady state conditions.

Consider the case of a Y:D30° power transformer with the following data (using a 1 A CT

secondary rating for the relay):

• Winding 1: 100 MVA, 220 kV, 250/1 CT ratio (rated current is 262.4 A, hence CT ratio

of 250/1)

• Winding 2: 100 MVA, 69 kV, 1000/1 CT ratio (rated current is 836.8 A, hence CT ratio

of 1000/1)

The 1000/1 CT ratio is not a perfect NAIO-03F match for the 250/1 ratio. The high-side CT produces a

secondary current of 262.5/250 = 1.05 A whereas the low-side CT produces a current of

0.837 A. The 745 automatically applies an amplitude correction factor to the Winding 2

currents to match them to the Winding 1 currents. The following illustrates how the

correction factor is computed:

(EQ 7.5)

The mismatch factor is therefore:

(EQ 7.6)

Winding 2 currents are divided by this factor to obtain balanced conditions for the

differential elements.

If this transformer were on line, fully loaded, and protected by a properly set 745 relay, the

actual current values read by the relay would be:

• Winding 1: 262.5 A ∠0° (this is the reference winding)
• Winding 2: 836.8 A ∠210° (30° lag due to transformer and 180° lag due to CT

connections)

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