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 at a selected value. The location of a regulator is determined by the type of loads and circuits
served. Regulators are available for ground or pole installation.
3.3.4.1 Bus Regulators. Bus regulation is often used when a substation has two or more
circuits with similar load characteristics and requirements. For such applications the regulator
installation controls the voltage on the substation bus rather than on individual circuits. Voltage
regulation of the bus can also be accomplished by equipping the station's power transformer with
a load tap changing (LTC) mechanism.
3.3.4.2 Feeder Regulators. Feeder regulators maintain a constant voltage on a particular
circuit with variation in load. They may be installed at a substation or located between the
substation and the load being served. On long lines, or lines with critical loads, two or more
regulator installations may be warranted in order to cope with the circuit requirements. These
may be located either on the main feeder or branch feeder circuits.
3.3.5 Regulator Control. Most modern regulators are motor-operated and automatically
controlled. Facilities are provided for the regulator to control the voltage at a point remote from
the regulator location. The components required to automatically control a motor-operated
regulator are:
(a)
Voltage sensing device.
(b)
Amplifying section.
(c)
Motor drive.
(d)
Line-drop compensator.
A voltage sensing device is connected through a potential transformer across the feeder or bus to
be regulated. The voltage sensing device, which may be either a voltage-regulating relay or a
static voltage sensor, operates a switch that controls the operating motor of the regulator. A
current transformer connected in series with the regulated circuit has its secondary winding
normally connected to a line-drop compensator. This line-drop compensator contains variable
resistance and reactance (each independently adjustable) which represents the impedance of a
regulated circuit. The voltage drop in the regulated circuit is, thus, easily detected by a
proportional voltage drop across the compensator. Once adjusted, the compensator permits the
regulator to hold constant voltage at a selected point on the circuit, regardless of load or power
factor.
3.3.6 Single- and Three-Phase Connections. Single-phase regulators are applied to control
the voltage on a single-phase circuit. They may, however, be applied to three-phase circuits and
have some advantage over three-phase units that regulate all three phases in the same manner.
Single-phase units, when applied to three-phase circuits, can be adjusted for separate regulation
levels. A three-phase unit can only be adjusted for an average value of the three phase
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