The multi-voltage control assessor for providing a set of standard voltages useful in testing electrical devices and systems is disclosed. The Multi-Voltage Control Assesor (MVCA) is a portable, small suitcase sized device containing transformers, switches, safety devices and cabling that, when operated safely by a competent person, can provide common voltages to power controls, relays and small devices intended for troubleshooting purposes. It can also temporarily substitute for a control transformer for a critical device, as necessary. It is not recommended for this to be a full time use, only until a suitable replacement can be installed.

An apparatus for a load tap changer includes a first primary winding electrically connected to a first contact, the first contact configured to connect to one of a plurality of taps in a load tap changer; a second contact, the second contact configured to connect to one of the plurality of taps in the load tap changer; a magnetic core; and a control circuit including: a secondary winding configured to magnetically couple to the first primary winding and the magnetic core; and an electrical network electrically connected to the secondary winding, the electrical network being configured to prevent magnetic saturation of the magnetic core during switching of the first or second contact.

A transformer arrangement comprises a primary winding and a secondary winding, which are magnetically coupled. The transformer arrangement also comprises a compensating arrangement, which is circuited to provide a link between a terminal of the primary winding and a terminal of the secondary winding. The compensating arrangement is configured such that a change of a magnetic flux through the primary winding and the secondary winding induces a voltage in the compensating arrangement. The compensating arrangement comprises at least one coupling capacitor configured to block a DC current and to pass a current caused by the induced voltage. The compensating arrangement is configured to at least partially compensate a current that is caused by an inter-winding capacitance between the primary winding and the secondary winding using the current caused by the induced voltage.

A transformer arrangement comprises a primary winding and a secondary winding, which are magnetically coupled. The transformer arrangement also comprises a compensating arrangement, which is circuited to provide a link between a terminal of the primary winding and a terminal of the secondary winding. The compensating arrangement is configured such that a change of a magnetic flux through the primary winding and the secondary winding induces a voltage in the compensating arrangement. The compensating arrangement comprises at least one coupling capacitor configured to block a DC current and to pass a current caused by the induced voltage. The compensating arrangement is configured to at least partially compensate a current that is caused by an inter-winding capacitance between the primary winding and the secondary winding using the current caused by the induced voltage.

A centralized voltage control apparatus is connected via a communication network to a plurality of local voltage control devices each controlling a corresponding voltage controller connected to a distribution line of a distribution system. The centralized voltage control apparatus includes: a voltage distribution determination unit that calculates a control variable for each of the voltage controllers on the basis of a measured value of voltage at each measurement point of the distribution line and a proper voltage range at each measurement point; and a tap position determination unit that gives a command value to each of the local voltage control devices on the basis of the control variable. At least a part of the proper voltage range at each measurement point is determined on the basis of an estimated value of a change in voltage in a section in which voltage is not measured on the distribution line.

A centralized voltage control apparatus is connected via a communication network to a plurality of local voltage control devices each controlling a corresponding voltage controller connected to a distribution line of a distribution system. The centralized voltage control apparatus includes: a voltage distribution determination unit that calculates a control variable for each of the voltage controllers on the basis of a measured value of voltage at each measurement point of the distribution line and a proper voltage range at each measurement point; and a tap position determination unit that gives a command value to each of the local voltage control devices on the basis of the control variable. At least a part of the proper voltage range at each measurement point is determined on the basis of an estimated value of a change in voltage in a section in which voltage is not measured on the distribution line.

Disclosed is a magnetic induction power supply device, which switches the unit coil having the smallest number of windings to a rectification unit at the initial operation, thereby preventing the parts damaged due to an excessive inrush voltage. The disclosed magnetic induction power supply device switches the unit coil having the smallest number of windings to the rectification unit when emergency power is applied from a first power supply unit or a second power supply unit. The second power supply unit can supply the power source induced in the unit coils to a sensing unit as the emergency power.

Disclosed is a magnetic induction power supply device, which switches the unit coil having the smallest number of windings to a rectification unit at the initial operation, thereby preventing the parts damaged due to an excessive inrush voltage. The disclosed magnetic induction power supply device switches the unit coil having the smallest number of windings to the rectification unit when emergency power is applied from a first power supply unit or a second power supply unit. The second power supply unit can supply the power source induced in the unit coils to a sensing unit as the emergency power.

An energy storage system is disclosed. The energy storage system includes at least one energy store, a power convertor for converting between a DC voltage present at the at least one energy store and an AC voltage, a transformer for transforming between the AC voltage and a line voltage of an energy supply network, and a control device for controlling the energy storage system. The transformer is switchable for setting a transformation ratio for converting between the AC voltage and the line voltage, wherein the control device is configured to set the transformation ratio of the transformer depending on the DC voltage present at the at least one energy store.

An energy storage system is disclosed. The energy storage system includes at least one energy store, a power convertor for converting between a DC voltage present at the at least one energy store and an AC voltage, a transformer for transforming between the AC voltage and a line voltage of an energy supply network, and a control device for controlling the energy storage system. The transformer is switchable for setting a transformation ratio for converting between the AC voltage and the line voltage, wherein the control device is configured to set the transformation ratio of the transformer depending on the DC voltage present at the at least one energy store.