METHOD AND SYSTEM FOR VOLTAGE REGULATION, CONTROL, PROTECTION AND MONITORING OF STATE OF ON-LOAD TAP CHANGERS OF POWER TRANSFORMERS, VOLTAGE REGULATORS, AND CAPACITOR BANKS

• US 20160147237A1
• Filed: 01/22/2016
• Published: 05/26/2016
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Eduardo Pedrosa Santos
• Original Assignee: Eduardo Pedrosa Santos
• Inventors: Santos, Eduardo Pedrosa
• Granted Patent: US 10,739,799 B2
• Time in Patent Office: Days
• CPC Class Codes: G05F 1/14 using tap transformers or tap changing inductors as final control devices
• CPC Class Codes: G05F 1/147 with motor driven tap switch
• CPC Class Codes: H02J 3/1878 using tap changing or phase shifting transformers
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

A method for voltage regulation, control, protection and monitoring of state of on-load tap changers of power transformers, voltage regulators, and capacitor banks comprising: uses a voltage regulation system that has sets of voltage regulation parameters available for programming by a user. Each of these sets is adjustable in an independent manner for a given prevailing load condition. The parameters include a desired rated voltage at a load; a voltage variance percentage allowed over and below rated voltage; time delay adjustments for CDC (15) actuation in order to correct voltage; choice of linear or reverse time delay type; and parameters referring to voltage drop in the line.

Claims

1. A METHOD FOR VOLTAGE REGULATION, CONTROL, PROTECTION AND MONITORING OF STATE OF ON-LOAD TAP CHANGERS OF POWER TRANSFORMERS, VOLTAGE REGULATORS, AND CAPACITOR BANKS comprising:

using a voltage regulation system (S) that has six or more sets (20A, 20B, 20C) of voltage regulation parameters (21) available for programming by a user, each of these sets (20A, 20B, 20C) being adjustable in an independent manner for a given prevailing load (L) condition, each set being the parameters (21), and wherein the parameters comprise;

a desired rated voltage at a load;

a voltage variance percentage allowed over and below rated voltage;

time delay adjustments for CDC (15) actuation in order to correct voltage;

choice of linear or reverse time delay type; and

parameters referring to voltage drop in the line.

2. The method of claim 1 wherein a selection of the set (20A, 20B, 20C) of voltage regulation parameters (21) is made by a dry contact input (5), wherein the selection of the set (20A, 20B, 20C) of voltage regulation parameters (21) is determined by a combination of open and closed contacts (5A, 5B, 5C) connected to the dry contact input (5).

3. The method of claim 2, wherein the combination of open and closed contacts (5A, 5B, 5C) is interpreted in a decimal manner, with each dry contact (5A, 5B, 5C) directly corresponds to a set of voltage regulation parameters (20A, 20B, 20C), such that, when the first contact (5A) is closed, a first set of parameters (20A) is selected, when the second contact (5B) is closed, a second set (20B) is selected.

4. The method of claim 2, wherein the combination of open and closed contacts (5A, 5B, 5C) is interpreted in a binary manner, with each individual contact (5A, 5B, 5C) corresponding to a bit that can assume the value 0 when the contact is open or 1 when the contact is closed, the combination of the several bits composing a binary number that, converted to a decimal number, indicates which set (20A, 20B, 20C) of voltage regulation parameters (21) is selected.

5. The method of claim 1 wherein the selection of the set (20A, 20B, 20C) of voltage regulation parameters (21) is accomplished by programming by the user, such programming comprising weekdays (22) and time ranges (23, 24) for activating each set (20A, 20B, 20C) of parameters;

for each set of parameters (20A, 20B, 20C) weekdays (22) from Sunday-to Saturday are selected, as well as a time range defined by an initial hour, minute and second (23) and a final hour, minute and second (24);

when the weekday indicated by a real-time clock (8) corresponds to one of the weekdays (22) selected to a given set of parameters (20A, 20B, 20C) and a present time indicated by the clock (8) is within the time range (23, 24) selected to the same set of parameters (20A, 20B, 20C), this set of parameters (20A, 20B, 20C) is then selected for use by the voltage regulation system (S).

6. A method for voltage regulation, control, protection and monitoring of state of on-load tap changers of power transformers, voltage regulators, and capacitor banks wherein a voltage regulation system (S) has two independent time delay parameters (31L, 31R) available for programming by a user, wherein one of the delay parameters (31R) is used when a measured load voltage (13) is below a preprogrammed rated voltage, and the other delay parameter (31L) is used when the measured load voltage (13) is above the preprogrammed rated voltage.

7. The method according to claim 6 wherein the voltage regulation system (S) has several parameters available for user programming of ranges of voltage deviation (31, 32, 33) in reference to the rated voltage, both below and above the rated voltage, and for each range of voltage deviation (31, 32, 33), the voltage regulation system (S) has two parameters available for user programming of a time delay (21) for OLTC (15) operation, some of the voltage deviations (31R, 32R, 33R) to be used when the measured load voltage (13) is too low, below the rated voltage, and the other (31L, 32L, 33L) to be used when the load voltage (13) is too high, above the rated voltage;

whenever the measured load voltage (13) is below or above an allowed tolerance margin (30), the voltage regulation system (S) compares the load voltage (13) to the ranges of voltage deviation (31, 32, 33), determines which of these ranges of voltage deviation correspond to measured load voltage (13) and selects a corresponding time delay parameter (31R, 32R, 33R, 31L, 32L, 33L) to be effectively used for voltage regulation in system (S) operation.

8. A method for voltage regulation, control, protection and monitoring of state of on-load tap changers of power transformers, voltage regulators, and capacitor banks, wherein a voltage regulation system (S) performs recording of measurements in non-volatile memory (9) according to parameters programmed by a user comprising:

a time interval for periodic recording;

selecting variables (9A) to be recorded in a memory (9), including;

a measured voltage (17), a load voltage (13), a load current (17′

) and an OLTC tap position (12), and calculated variables including;

active and reactive power, frequency and load power factor;

a recording mode (9B) for each of the variables (9A) selected for recording, the recording mode (9B) selected from a group including;

instantaneous value of the variable, average value of the variable calculated during the interval since last recording, root mean square of the variable calculated during the interval since last recording, maximum value of the variable observed during an interval since last recording or minimum value of the variable observed during the interval since last recording; and

selecting more than one recording mode (9B) for each of the variables (9A) selected for recording.

9. A method for voltage regulation, control, protection and monitoring of state of on-load tap changers of power transformers, voltage regulators, and capacitor banks, wherein a voltage regulation system (S) performs the OLTC Maintenance Assistant function by measuring an OLTC tap position measurement through a tap measuring input (12) comprising:

counting a total number of OLTC (15) operations since a beginning of OLTC operation, the count being increased every time the OLTC tap position measurement input (12) changes;

counting a partial number of OLTC (15) operations since a last maintenance performed on the OLTC, the counter being increased every time the OLTC tap position measurement input (12) changes;

wherein both a total counting and a partial counting are increased by one unit every time the OLTC tap position measurement input (12) changes, except for tap positions previously selected and programmed by a user with an specific number to be used to increase both counters;

wherein both the total counting and the partial counting are recorded in a voltage regulation system (S) non-volatile memory (9);

wherein both the total counting and the partial counting can have values programmed by the user, so as to allow an application of the OLTC Maintenance Assistant function with old OLTCs;

wherein based on a user programming of a number of operations after which OLTC maintenance must be performed, the voltage regulation system (S) issues a warning indicating a need for OLTC maintenance when a partial operation counting is equal or higher than the number of operations after which OLTC maintenance must be performed;

wherein the voltage regulation system (S) calculates an average number of OLTC operations per day by dividing a number of operation in the last X days by X elapsed days, X being a time interval programmable by the user;

wherein the voltage regulation system (S) calculates a remaining time for reaching the number of operations for OLTC maintenance, according to a formula;

Y=((No. of operations for maintenance)+(partial operation counter))/(Average daily operations);

wherein the voltage regulation system (S) issues a maintenance warning indicating that OLTC maintenance will be necessary within Y days, when a value calculated for Y is equal or lower than a number of days for advanced maintenance warning programmed by the user; and

wherein the maintenance warnings will remain active in the voltage regulation system (S) until the user performs a manual warning reset at a keyboard (3), informing the voltage regulation system (S) that maintenance has been performed;

once the manual reset is made, partial operation counting since the last maintenance is zeroed and warnings for maintenance are switched off.

10. The method of claim 9, wherein the voltage regulation system (S) performs the OLTC Maintenance Assistant function by measuring the OLTC tap position through the tap measuring input (12) and a load current (17′

), wherein;

every time the OLTC (15) tap position measurement input (12) changes the voltage regulation system (S) squares the load current measurement and adds the squared value to a previous value in a total switched current sum recorder since a beginning of the CDC operation, which is stored in non-volatile memory (9);

every time the OLTC (15) tap position measurement (12) changes the voltage regulation system (S) takes squares a load current measurement at a time of a tap change and adds the squared value to the already existing value in the partial switched current sum recorder since the last maintenance performed on the OLTC (15), which is stored in non-volatile memory (9) in the voltage regulation system (S);

both the total and the partial recorder can have its values programmed by the user, so as to allow an application of the OLTC Maintenance Assistant with old OLTCs;

based on a user programming of a limit value for a sum of switched current after which OLTC (15) maintenance must be performed, the voltage regulation system (S) issues a warning indicating a need for OLTC maintenance when the partial sum recorder is equal or higher than the limit value for maintenance;

the voltage regulation system (S) calculates an average per day increment of sum of switched current by dividing an increment in a switched current in a last W days by W elapsed days, W being a time interval programmable by the user;

the voltage regulation system (S) calculates a remaining time for reaching a limit value of a sum of switched current for OLTC maintenance, according to;

Z=((Sum value for maintenance)+(partial sum recorder))/(Daily increment average in sum)

the voltage regulation system (S) issues a warning indicating that the OLTC maintenance will be necessary within Z days, when Z is equal or lower than a number of days for advanced maintenance warning programmed by the user; and

maintenance warnings will remain active in the voltage regulation system (s) until the user performs a manual warning reset at a keyboard (3), informing the voltage regulation system (s) that maintenance has been performed;

once a reset is made, a partial recorder of switched current since the last maintenance is zeroed and warnings for maintenance are switched off.