SMART VOLTAGE REDUCTION AND REVERSE POWER OPERATING MODE DETERMINATION FOR LOAD TAP CHARGING TRANSFORMERS AND VOLTAGE REGULATORS

• US 20150185743A1
• Filed: 12/29/2014
• Published: 07/02/2015
• Est. Priority Date: 12/27/2013
• Status: Active Grant

• Current Assignee: Hubbell Power Systems Incorporated (Hubbell, Inc.)
• Original Assignee: Beckwith Electric Company Incorporated (Hubbell, Inc.)
• Inventors: McFetridge, Robert, Yalla, Murty
• Granted Patent: US 11,320,845 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G05F 1/10 Regulating voltage or current G05F1/02 takes precedence; for electric railways B60M3/02

Abstract

The present disclosure relates to a system for using load tap changing (LTC) transformers and voltage regulators to more accurately reduce the voltage in a power transmission system. It further relates to a system for determining the operating mode for LTC transformers and VRs during reverse power flow. Corresponding methods are also disclosed. The various components of the present system, and the manner in which they interrelate, are more fully described hereinafter.

Claims

1. A system for more accurately reducing applied voltages comprising:

a power distribution system, the distribution system including a power generator and a load, the power generator delivering an applied voltage at a predetermined level to the load;

the power distribution system including a load tap changing (LTC) transformer or voltage regulator, the LTC transformer or voltage regulator including tap selector switches, the tap selector switches selectively engaging a contact to thereby lower the applied voltage, the tap selector switches reducing the applied voltage in set increments;

a LTC controller for controlling the operation of the tap selector switches, the LTC controller establishing an upper band edge voltage, a lower band edge voltage, and a bandcenter that is between the upper and lower band edge voltages, the LTC controller functioning to keep the applied voltage between the upper and lower band edge voltages via the operation of the tap selector switches;

means for temporarily disabling the upper band edge voltage and temporarily designating the bandcenter as the upper band edge voltage whereby the tap selector switches operate in set increments to reduce the applied voltage to a level that is between the redesigned bandcenter and the lower band edge.

2. The system as described in claim 1 wherein the means for temporarily disabling can be used to disable the lower band edge voltage and temporarily designate the bandcenter as the lower band edge voltage whereby the tap selector switches operate in set increments to increase the applied voltage to a level that is between the redesigned bandcenter and the upper band edge voltage.

3. The system as described in claim 1 wherein the means for temporarily disabling is a controller incorporating a microprocessor and memory.

4. The system as described in claim 3 wherein the microprocessor calculates the upper band edge using the formula (bandcenter+bandwidth/2) and calculates the lower band edge 3 using the formula (bandcenter−

bandwidth/2).

5. A method for varying voltage with a power distribution system, the method employing a controller for determining and storing upper and lower band edge voltages, a bandcenter, and bandwidth, the method comprising the following steps:

monitoring by way of the controller the var flow while in a voltage reduction mode;

determining by way of the controller when the var flow is leading and when such a determination is made linearly shifting the bandcenter down based on the amount of leading vars;

operating the controller to maintain the voltage within upper and lowerband edge voltages.

6. The method as described in claim 5 comprising the further step of using the controller to determine when the var flow is lagging and when such a determination is made linearly shifting the bandcenter up based on the var flow.

7. A system for more accurately reducing applied voltages comprising:

a power distribution system including switches for selectively lowering or raising the applied voltage;

a microprocessor for controlling the operation of the switches, the microprocessor establishing upper and lower band edge voltages, and a bandcenter that is between the upper and lower voltages, the microprocessor functioning to keep the applied voltage between the upper and lower band edge voltages via the operation of the switches;

the microprocessor functioning to temporarily disable the upper band edge voltage and temporarily designating the bandcenter as the upper band edge voltage whereby the switches operate in set increments to reduce the applied voltage to a level that is between the redesigned bandcenter and the lower band edge voltage.

8. A method for automatically detecting the operating mode of a LTC/VR controller during periods of reverse power flow in a power distribution system, the method utilizing tapchanges for varying the applied voltage on the basis of tap changes and tap commands, the operating modes including a reverse regulate mode wherein the tap change commands are reversed and a distributed generation mode wherein the tap change commands operate normally, the method comprising the following steps:

measuring the load voltage within the power distribution system a short time before and a short time after a tap operation, storing the difference in the voltage load as a tap delta voltage;

if the tap delta voltage is greater than a set value, keeping the LTC/VR controller in the distributed generation mode;

if the tap delta voltage is less than or equal to a set value for two consecutive tap operations, the LTC/VR controller is changed from distributed generation mode to reverse regulate mode.

9. The method of claim 8 wherein the set value is 0.4 volts.