ABB REF615 L User Manual

Distortion measurement
The distortion measurement module measures harmonics up to the 11th harmonic.
The total harmonic distortion THD for voltage is calculated from the measured
harmonic components with the formula
THD
U
U
k
k
N
=
=
∑
2
2
1
GUID-83A22E8C-5F4D-4332-A832-4E48B35550EF V1 EN (Equation 98)
U
k
k
th
harmonic component
U
1
the voltage fundamental component amplitude
Demand calculation
The demand value for THD is calculated separately for each phase. If any of the
calculated demand THD values is above the set alarm limit THD alarm limit, the
ALARM output is activated.
The demand calculation window is set with the Demand interval setting. It has
seven window lengths from "1 minute" to "180 minutes". The window type can be
set with the Demand window setting. The available options are "Sliding" and "Non-
sliding".
The activation of the BLOCK input blocks the ALARM output.
10.2.5 Application
VMHAI provides a method for monitoring the power quality by means of the
voltage waveform distortion. VMHAI provides a short-term three-second average
and long-term demand for THD.
10.2.6 Signals
Table 647: VMHAI Input signals
Name
Type Default Description
U_A_AB SIGNAL 0 Phase-to-earth voltage A or phase-to-phase
voltage AB
U_B_BC SIGNAL 0 Phase-to-earth voltage B or phase-to-phase
voltage BC
U_C_CA SIGNAL 0 Phase-to-earth voltage C or phase-to-phase
voltage CA
BLOCK BOOLEAN 0=False Block signal for all binary outputs
Section 10 1YHT530004D05 D
Power quality measurement functions
770 615 series
Technical Manual

ABB REF615 L Specifications

General

Type	Feeder Protection Relay
Rated Frequency	50/60 Hz
Weight	Approx. 1.5 kg
Communication Protocols	IEC 61850, Modbus RTU, DNP3
Protection Functions	Overcurrent, Earth fault, Thermal overload, Under/Over voltage, Under/Over frequency
Enclosure	IP20