Substation load distribution monitor system

• US 5,179,376 A
• Filed: 02/28/1991
• Issued: 01/12/1993
• Est. Priority Date: 02/28/1991
• Status: Expired due to Fees

• Current Assignee: Imperial Bank (Imperial Bancorp)
• Original Assignee: Systems Analysis & Integration, Inc.
• Inventors: Pomatto, Lawrence A.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Krakovsky, Michael
• Application Number:
  US07/663,104
• Time in Patent Office: 684 Days
• Field of Search: 340/870.02, 340/310 A, 340/870.05, 324/83 R, 324/83 D, 324/85, 324/126, 324/127, 361/30, 361/35, 361/79-81, 364/571.02, 364/178, 364/483
• US Class Current: 340/870.02
• CPC Class Codes: H02J 13/00017 using optical fiber
• CPC Class Codes: H02J 13/00028 involving the use of Internet protocols
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/16 Electric power substations
• CPC Class Codes: Y04S 40/124 using wired telecommunication networks or data transmission busses

Abstract

The monitoring and control system of the present invention provides a distributed intelligence, data acquisition and control system which collects and analyzes large amounts of data representing power usage from a power distribution substation. The system also provides the capability of various control functions for the substation. The system provides communications capabilities between local devices and also with a remote computer. The system provides real time monitoring of power usage and real time control of various functions in the substation.

Claims

1. A substation monitoring system wherein the substation distributes power through power equipment carrying a voltage waveform and a current waveform, wherein the power equipment also has associated protection circuits carrying a current waveform which is stepped down from, but proportional to, the current waveform in the power equipment, said system comprising:

at least one system controller;

a power converter which steps down said power equipment voltage waveform;

a high-accuracy, split-core current transformer permanently, yet detachably mounted on one leg of said protection circuit, said current transformer providing a stepped down current waveform, stepped down from, but proportional to, the current waveform in the power equipment;

a sampler which accepts the stepped down current waveform from said current transformer and converts the stepped down current waveform into a digital representation of said current waveform, and which accepts the stepped-down power equipment voltage waveform and converts the voltage waveform to a digital representation of said voltage waveform;

at least one microcontroller based data unit in communication with said system controller, wherein said data unit is coupled to the sampler and accepts the digital representations of the voltage and current waveforms from said sampler and determines from the digital representations of the voltage and current waveforms, a relative phase angle between the sampled current waveform and the sampled voltage waveform, and wherein the data unit further utilizes the digital representations of the voltage and current waveforms to calculate the power, power factor, and volt amperes reactive, distributed by said power equipment; and

a communications link which sends said calculations to a remote computer.

2. The substation monitoring system of claim 1, wherein current in said protection circuit is in the range of 0-5 Amps, and the stepped down current waveform from said split-core current transformer is in the range of 0-0.5 mA.

3. The substation monitoring system of claim 2, wherein the split-core current transformer is calibrated upon installation such that is has a repeatable accuracy of 1% or better in the current range during system operation.

4. A method of monitoring substation power equipment carrying a voltage waveform and a current waveform, wherein the power equipment also has associated protection circuits carrying a current waveform which is stepped down from, but proportional to, the current waveform in said power equipment, said method comprising:

providing at least one system controller;

providing at least one data acquisition controller in communication with said system controller;

stepping down said power equipment voltage waveform;

permanently, yet detachably mounted a split-core current transformer on one leg of said protection circuit, said current transformer providing a current waveform, stepped down from, but proportional to, the current waveform in said power equipment;

sampling the current waveform provided by said current transformer and converting the current waveform into a digital representation of the current waveform for further processing by said system controller and said data acquisition controller;

sampling said stepped-down power equipment voltage waveform and converting said voltage waveform to a digital representation of the voltage waveform; and

determining a relative phase angle between the sampled current waveform and the sampled voltage waveform by utilizing the digital representation of the voltage and current waveforms;

calculating the power, power factor and volt amperes reactive distributed by said power equipment by using the sampled digital representations of the voltage and current waveforms; and

transmitting the calculations to a remote computer.

5. A method of monitoring substation power equipment carrying a voltage waveform and a current waveform, wherein the power equipment also has associated protection circuits carrying a current waveform which is stepped down from, but proportional to, the current waveform in said power equipment, wherein the voltage and current waveforms are alternating current sine waves said method comprising:

providing a at least one system controller;

providing at least one intelligent data unit in communication with said system controller;

stepping down the power equipment voltage waveform;

permanently, yet detachably mounting a high-accuracy, split-core current transformer on at leas one leg of said protection circuit, said current transformer providing a current waveform stepped down from, but proportional to, the current waveform in said power equipment;

sampling the current waveform provided by said current transformer and converting the current waveform into a digital representation of the current waveform for further processing by said data unit and said system controller;

sampling said stepped-down power equipment voltage waveform and converting said voltage waveform to a digital representation of the power equipment voltage waveform; and

determining a relative phase angle between the sampled current waveform and the sampled voltage waveform sine waves by utilizing the digital representations of the voltage and current waveforms.

6. The method of monitoring of claim 5, wherein said step of detachably mounting comprises the steps of:

removing a detachable base plate of said split-core current transformer;

positioning said one leg of said protection circuit within the split-core current transformer; and

re-attaching the detachable base plate.

7. The method of monitoring of claim 5, wherein said system controller communicates with a remote computer.

8. The method of monitoring of claim 5, further comprising the steps of:

calculating the power, volt amperes, power factor, and volt amperes reactive, associated with said power equipment by utilizing the digital representations of the voltage and current waveforms; and

transmitting said calculations to a remote computer.

9. A method of monitoring substation power equipment carrying a voltage and a current in the form of sine waves, wherein the power equipment also has associated protection circuits carrying a current in the form of sine waves which is stepped down from, but proportional to, the current flowing in said power equipment, said method comprising the steps of:

stepping down the power equipment voltage;

stepping down the protection circuit current with a split-core current transformer by detachably mounting the split-core current transformer on a leg of the protection circuit, such that a current provided from the split-core transformer is proportional to the current flowing in the power equipment;

sampling with a sampler the current provided by said current transformer and converting the current into a digital representation with a single converter, wherein the sampling and converting of the current provides a first plurality of raw sample points representative of the current sine waves in said power equipment;

sampling with said sampler said stepped-down power equipment voltage and converting said voltage to a digital representation of the voltage with said single converter, wherein the sampling and converting of the voltage provides a second plurality of raw sample points representative of the voltage sine waves in said power equipment said second plurality not being synchronized in time with the first plurality of raw sample points;

assigning corresponding time clicks for each of the first plurality and the second plurality of raw sample points; and

transforming the first and the second plurality of raw sample points into a first transformed synchronized distribution and a second transformed synchronized distribution, wherein the first and second transformed distributions comprises corresponding synchronized sample points which form a representation of the voltage and current sine waves of said power equipment.

10. The method of monitoring power equipment of claim 9, the method further comprising the steps of:

calculating a first mean of the first transformed distribution and a second means of the second transformed distribution;

determining the time clicks for points in the first transformed distribution which equal the first mean;

determining the time clicks for points in the second transformed distribution which equal the second mean;

averaging the difference in time clicks between consecutive points in the first transformed distribution which equal the first mean to determine an average cycle time for said first transformed distribution; and

averaging the difference in time clicks between consecutive points in the second transformed distribution which equal the second mean to determine an average cycle time for said second transformed distribution.

11. The method of monitoring substation power of claim 10, the method further comprising the step of:

calculating the difference between the average cycle time for said first distribution and the average cycle time for said second distribution to determine a relative phase time between said first and said second transformed distributions.

12. The method of monitoring substation power of claim 11, the method further comprising the steps of:

calculating the root means squared voltage and the root means squared current for said power equipment from the first and second transformed distributions; and

calculating a power factor for said power equipment corresponding to the relative phase between the first and the second transformed distributions.

13. The method of monitoring substation power of claim 9, the method further comprising the steps of:

determining an average cycle time for said first transformed distribution;

determining an average cycle time for said second transformed distribution; and

determining a relative phase time between said first and said second transformed distributions.

14. The method of monitoring substation power of claim 13, the method further comprising the steps of:

calculating the root means squared voltage and the root mean squared current of the power equipment from the first and second transformed distributions; and

calculating a power factor for the power equipment corresponding to the relative phase between the first and the second transformed distributions.

15. A method of monitoring substation power distributed by power equipment carrying a voltage and a current in the form of sine waves, wherein the power equipment also has associated protection circuits carrying a current which is stepped down from, but proportional to, the current flowing in said power equipment, said method comprising the steps of:

stepping down the power equipment voltage;

stepping down the protection circuit current with a split-core current transformer by detachably mounting the split-core current transformer on a leg of said protection circuit, such that a current provided from the split-core transformer is proportional to the current flowing in the power equipment;

sampling a representation of the current provided by said current transformer and converting said representation into digital form with a converter, wherein the sampling and converting of the representation of the current provides a first plurality of raw sample points representative of the current flowing in said power equipment;

sampling the stepped-down power equipment voltage and converting said voltage to digital form with said converter, wherein the sampling and converting of the voltage provides a second plurality of raw sample points representative of the voltage in said power equipment, said first plurality of raw sample points not being synchronized in time with said second plurality of raw sample points; and

transforming the first and the second plurality of raw sample points into a first transformed synchronized distribution and a second transformed synchronized distribution wherein the first transformed distribution comprises a first plurality of data points and the second transformed distribution comprises a second plurality of data points, said first plurality of data points being synchronized in time to the second plurality of data points.

16. A monitoring system for use with power equipment carrying related voltage and current sine waves, the system comprising:

at least one split-core current transformer permanently, yet detachably mounted on one leg of a protection circuit for the power equipment;

a sampler which obtains alternate raw sample points of the related voltage and current sine waves and converts the raw sample points to digital form; and

data acquisition equipment which accepts the digital raw sample points from the sampler, transforms the digital raw sample points into transformed synchronized distributions having a plurality of synchronized digital data points, wherein said transformed distributions provide digital representations of the related voltage and current sine waves;

said data acquisition equipment comprising a microcontroller based data unit in communication with the sampler, wherein said data unit is coupled to the sampler and accepts the digital representations of the voltage and current sine waves, wherein the data unit determines a relative phase angle between the related voltage and current sine waves by comparing the digital representations of the related voltage and current sine waves.

17. A substation monitoring system wherein the substation distributes power through power equipment carrying a voltage waveform and a current waveform, wherein the power equipment also has associated protection circuits carrying a current waveform which is stepped down from, but proportional to, the current waveform in the power equipment, said system comprising:

a power converter which steps down said power equipment voltage waveform;

a split-core current transformer permanently, yet detachably mounted on one leg of said protection circuit, said current transformer providing a stepped down current waveform, stepped down from, but proportional to, the current waveform in the power equipment, said stepped down current waveform being in the range of 0-0.5 mA, said split-core current transformer further being calibrated within the substation monitoring system to have a repeatable accuracy of 1% or better in the 0-0.5 mA stepped down current waveform range during system operation;

a sampler which accepts the stepped down current waveform from said current transformer and converts the stepped down current waveform into a digital representation of said current waveform, and said sampler accepting the stepped down power equipment voltage waveform and converting the voltage waveform to a digital representation of said voltage waveform;

at least one microcontroller based data unit coupled to the sampler, said data unit accepting the digital representations of the voltage and current waveforms from said sampler and determining from the digital representations of the voltage and current waveforms, a relative phase angle between the sampled current waveform and the sampled voltage waveform, and wherein the data unit further utilizes the digital representations of the voltage and current waveforms to calculate the power, power factor, and volt amperes reactive, distributed by said power equipment; and

a communications link which sends said calculations to a remote computer.

18. A substation monitoring system wherein the substation distributes power through power equipment carrying a voltage waveform and a current waveform, wherein the power equipment also has associated protection circuits carrying a current waveform which is stepped down from, but proportional to, the current waveform in the power equipment, said system comprising:

a power converter which steps down said power equipment voltage waveform;

a split-core current transformer detachably mounted on one leg of said protection circuit, said current transformer providing a stepped down current waveform, stepped down from, but proportional to, the current waveform in the power equipment;

a sampler which accepts the stepped down current waveform from said current transformer and converts the stepped down current waveform into a digital representation of said current waveform, said sampler further accepting the stepped down power equipment voltage waveform and converting the voltage waveform to a digital representation of said voltage waveform; and

at least one microcontroller based data unit coupled to the sampler, said data unit accepting the digital representations of the voltage and current waveforms from said sampler and determining from the digital representations of the voltage and current waveforms, a relative phase angle between the sampled current waveform and the sampled voltage waveform, and wherein the data unit further utilizes the digital representations of the voltage and current waveforms to calculate the power, power factor, and volt amperes reactive, distributed by said power equipment.