Date Code 20191014
Information Sheet
SEL-734W and SEL-WCS
SEL-734W and SEL-WCS
The SEL-734W Wireless Capacitor Bank Control is a system that includes the
controlling device (SEL-734W) and the line current sensors (8340). The sensors
report line in the current via radio transmission. The SEL-734W includes a radio
receiver used solely for the purpose of receiving the transmissions from the line
current sensors. A capacitor bank control uses measurements of voltage and cur-
rent on the distribution lines of an electric utility to determine if the distribution
of electric power can be made more efficient by connecting a capacitor from the
phase to the neutral conductors of the distribution system. Based on user-select-
able settings, the SEL-734W will drive the capacitor bank switches to connect/
disconnect the capacitors from the power lines of the distribution system. Opera-
tion of the SEL-734W is the same as the operation of the SEL-734B with the
exception of how the line currents are read.
The SEL-734B accepts wires carrying low-level voltages that are an analog rep-
resentation of the current in each of the power system conductors. These wires
are connected to sensors attached to the power lines, with the sensors converting
the current to low-level voltages known as low-energy analog (LEA) signals. For
information that is common to both the SEL-734B and the SEL-734W including
installation, operation, and settings, refer to the documents found at
www.selinc.com/products/734B. For information on how the SEL-734W and the
SEL-734B differ, refer to the sections below.
SEL Wireless Current Sensor (SEL-WCS)
Overview
The SEL-WCS provides measurement of power line current both for the funda-
mental frequency and harmonic frequencies (up to the 15th). This sensor is pro-
vided in a package that is easy to mount using a hot stick and requires no wiring
to the capacitor bank control or to a power source. Power is harvested from the
magnetic field surrounding the power line when current is flowing. The
SEL-WCS operates without the use of a battery, eliminating that maintenance
concern while allowing for a smaller, simpler device. The SEL-WCS measures
the current and updates the SEL-734W periodically, making sure that it has
enough stored energy to complete the measurement and transmit the information
to the SEL-734W before beginning the measurement process. The SEL-734W
provides a measurement range of 2 A to 1000 A. The SEL-WCS is paired to an
SEL-734W by settings selections made on both devices.
Current Measurements
Measurements are made by the sensor and sent to the SEL-734W about once
every 1.1 seconds or as harvested energy allows, whichever is slower. The
SEL-734W will use the last value transmitted in all reporting, calculations, and
actions involving the current until the next update of the current. If the
SEL-734W has not received a recognizable update within a certain timeframe,
the current value is set to zero and stays at zero until the next successful update.
A switch-selectable setting for the SEL-WCS tells the sensor whether it should
calculate the magnitude and phase values of the harmonics. By selecting the
SEL-734W Wireless Capacitor Bank Control
and SEL-WCS Wireless Current Sensor
