1. HJ International Latin America, Inc.
Installed capacity of Distribution Transformers. The situation and a proposal of solution.
HJ International Latin America, Inc.

2. Presentation of the situation
There is an excess of installed capacity of distribution transformers
HJ International Latin America, Inc.

3. HJ International Latin America, Inc.
An interesting ratio
Invoiced energy, Gwh per year
Fi =
CITD * fp * 24 * 360
CITD: Installed capacity in Distribution Transformers, GVA
fp: Global system power factor
HJ International Latin America, Inc.

4. Determining the magnitude of the Over-Capacity
One indicator of the over-capacity is the ratio between the installed capacity of Power Transformers in the Substations at the end of the transmission lines and …..
HJ International Latin America, Inc.

5. Determining the magnitude of the Over-Capacity
…. the total installed capacity of distribution transformers reducing medium voltage to low voltage levels.
HJ International Latin America, Inc.

6. Determining the magnitude of the Over-Capacity
In most cases, the ratio R :
Installed Capacity of Distribution Transformers
R =
Installed Capacity of Power Transformers
> 2.0
HJ International Latin America, Inc.

7. Something to think about….
Since the flow of energy in the system is the same for Power and Distribution Transformers…..
AVERAGE LOAD AVERAGE LOAD DISTRIBUTION POWER TRANSFORMERS TRANSFORMERS = R
HJ International Latin America, Inc.

8. HJ International Latin America, Inc.
Now, transformer size can be selected based on maximum load (Utilization Factor, Fu)...
Max Load
Fu =
Transf. Size
HJ International Latin America, Inc.

9. …or based on the rms equivalent load...
TRANSFORMER AVERAGE LOAD :
rms equiv. load
La =
Transf. size
TRANSFORMER OVERSIZE
HJ International Latin America, Inc.

10. HJ International Latin America, Inc.
Then we realize that...
If transformers are selected just thinking of maximum load…
…this conduces to select capacities much higher than the actually needed.
Transformer sizes should be selected as possible based on the average load taken from the actual load curve (projected)…
It is important to take advantage of the transformer overload capacity.
HJ International Latin America, Inc.

11. Oversize magnitude comes from...
Ratio R, commented before, and
A ratio K depending on the load curve and defined as...
K = Fu / La = Maximum load / Average load
Maximum oversize magnitude comes from the product given by…….
OSmax = R * K
HJ International Latin America, Inc.

12. Something more to think about….
Since the flow of energy in the system is the same for Power and Distribution Transformers…..
AVERAGE LOAD Fu OF THE DISTRIBUTION POWER TRANSFORMERS TRANSFORMERS =
R * K
HJ International Latin America, Inc.

13. HJ International Latin America, Inc.
A typical value for K is This makes OSmax = 4.8 Thus, the average load of distribution transformers in the system can be so low as….
HJ International Latin America, Inc.

14. Immediate goal is...
To increase the average load of Distribution Transformers in the System.
TIP
Importance of the load losses
in this process
HJ International Latin America, Inc.

15. Average Load of Distribution Transformers in the system (Instance)
Average transformer ratings may be reduced in the system by factors from 2 up to 5 !!
HJ International Latin America, Inc.

16. HJ International Latin America, Inc.
However….
There are 2 aspects to be taken into account as increasing average load of distribution transformers
TRANSFORMER LOSSES
TRANSFORMER FAILURES
HJ International Latin America, Inc.

17. Increasing or reducing through higher La in the system??
LOSSES COST...
Increasing or reducing through higher La in the system??
HJ International Latin America, Inc.

18. WHERE WE ARE TODAY INDICATES OUR COMPROMISE
CURRENT SITUATION
20 %
WHERE WE SHOULD BE
60 A 75 %
HJ International Latin America, Inc.

19. UNLESS THE TRANSFORMER BE ADEQUATELY PROTECTED AGAINST OVERLOADS !!
TRANSFORMER FAILURES
It is experienced an increment of overload failures along with a higher “La” in the system
UNLESS THE TRANSFORMER BE ADEQUATELY PROTECTED AGAINST OVERLOADS !!
HJ International Latin America, Inc.

20. Our proposal of solution is...
THE SELF PROTECTED TRANSFORMER
To increase the Average Load “La” without increasing overload failures
To allow the reduction of the Over-Capacity factor “R” along with the losses in the system without increasing other related costs
To reduce installation costs
To get a significant reduction of the overall transformers failure rate in the distribution system
HJ International Latin America, Inc.

21. HJ International Latin America, Inc.
P – A – U – S - E
HJ International Latin America, Inc.

22. SUMMARY OF THE SELF - PROTECTION PRINCIPLES
A GUIDE THAT SHOWS THE MAIN CONCEPTS TO SUCCESSFULLY INTRODUCE THE SELF - PROTECTION PHILOSOPHY
HJ International Latin America, Inc.

23. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 1
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

24. HJ International Latin America, Inc.
Using Self Protected Transformers is not only to add some components to the transformer…!!
BREAKER
ARRESTER
SIGNAL
LIGHT
FUSES
OPERATING HANDLE & EMERGENCY OVERLOAD
HJ International Latin America, Inc.

25. …it is to use a COMPLETE philosophy to protect and handle with...
THE TRANSFORMERS...
HJ International Latin America, Inc.

26. …it is to use a COMPLETE philosophy to protect and handle with...
...THE DISTRIBUTION SYSTEM...
HJ International Latin America, Inc.

27. …it is to use a complete philosophy to protect and handle with...
...AND THE CUSTOMERS !
HJ International Latin America, Inc.

28. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 2
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

29. Main transformer protecting tasks, including selection and coordination…
ARE TRANSFORMER MANUFACTURER ISSUES !!
BLACK BOX
CONVENTIONAL
SELF - PROTECTED
HJ International Latin America, Inc.

30. HJ International Latin America, Inc.
This causes...
Simplification of the transformers installation
Less warranty discussions between Utility and transformer manufacturer
Longer warranty terms
HJ International Latin America, Inc.

31. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 3
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

32. HV Fuse should be internally connected
THIS TO AVOID:
Fuse rating changed
Dangerous operation of damaged units
Miss-coordination of the transformer protecting devices
HJ International Latin America, Inc.

33. This arises a question...
IS IT NEEDED TO INSTALL THE FUSED CUT-OUT WITH EVERY TRANSFORMER ?
HJ International Latin America, Inc.

34. Some responses from self-protecting principles to this question are:
The load-break operation is made in LV side by operating the breaker operating handle (this is a safer operation)
Fuse has one main and one secondary function:
MAIN FUNCTION of the fuse is to act like an over-current protection by isolating a failed transformer from the system.
SECONDARY FUNCTION is to act like a back-up protection
To eliminate the use of fused Cut-out with every transformer it is important to have well trained people to handle with energized lines
It is strongly recommended to use Wildlife Guards in those case fused Cut-out is not used
HJ International Latin America, Inc.

35. Cut-outs continue to be an essential part of the distribution circuits for circuit maintenance proposals...
SPECIALLY AT THE BEGINNING OF THE CIRCUIT BRANCHES
HJ International Latin America, Inc.

36. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 4
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

37. Signal Light is an essential part of one integral self-protecting policy to get an effective load management
OFF
SHOWS A NORMAL LOAD OR CIRCUIT SITUATION ON
SHOWS AN ABNORMAL LOAD OR CIRCUIT SITUATION
HJ International Latin America, Inc.

38. HJ International Latin America, Inc.
The signal light is an essential part of an integral self-protection policy
It’s an easy and economical way to detect any thermal abnormal operating condition without the need of costly measuring and monitoring methods
It operates like a PREVENTIVE ALARM without customer disconnection
It can be factory calibrated to meet the actual load curve requirements and the desired trip conditions
It’s a very effective way to detect energy robbery
If attended, it’s a very effective way to reduce non-planned loadbreaks
HJ International Latin America, Inc.

39. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 5
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

40. Arresters are to be installed at the transformer’s tank
IN CONVENTIONAL TRANSFORMERS CUT-OUT FUSES WOULD BE INSTALLED UP- STREAM
HJ International Latin America, Inc.

41. HJ International Latin America, Inc.
Arresters arranged far from transformer tank makes the transformer not right protected
HJ International Latin America, Inc.

42. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 6
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

43. Transformer Load Management (TLM) in service is to be made
Any overload, at peak hours, above the maximum allowed is to be detected and alarm is to be given by the transformer itself
Any transformer giving reiterative alarm information is to be changed for a larger capacity unit. Before that, a load analysis is to be made
According to above change policy a SELECTIVE transformers load analysis in the system is made. Signal light acts like a sample selector.
Overload capacity of the transformers is to be actually used
HJ International Latin America, Inc.

44. THE SELF - PROTECTION PHILOSOPHY
PRINCIPLE
# 7
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

45. Assets Management of the transformers in service is to be made
LIKE ANY OTHER ASSET, TRANSFORMER’S LIFE AT THE INSTALLATION PLACE IS TO BE PLANNED ACCORDING TO THE LOAD AND TO A REPLACEMENT POLICY
AN INVENTORY ROTATION POLICY SHOULD BE DEFINED !
HJ International Latin America, Inc.

46. THE SELF - PROTECTION PHILOSOPHY
OTHER PRINCIPLES & FINAL ISSUES
IMPORTANT NOTE
APPLICABILITY OF THESE PRINCIPLES MAY VARY DEPENDING ON THE PARTICULAR CIRCUMSTANCES OF THE UTILITY
HJ International Latin America, Inc.

47. HJ International Latin America, Inc.
UNBALANCED LOADS
UNBALANCED LOADS ARE EASILY DETECTED IN A 3F BANK OF 1F SELF PROTECTED UNITS.
UNBALANCED LOADS IN 3F BREAKERS CAN CAUSE PREMATURE SIGNAL LIGHT OR BREAKER TRIP.
FOR THIS REASON OUR PRINCIPLE # 6 CALLS TO MAKE A LOAD ANALYSIS IN EACH CIRCUIT CAUSING SIGNAL LIGHT OR BREAKER TRIP.
AGAIN SELF PROTECTION PHILOSOPHY APPLICATION ACTS LIKE PREVENTIVE WAY TO DETECT SYSTEM PROBLEMS WITHOUT HIGH COSTS INTERRUPTIONS.
HJ International Latin America, Inc.

48. Making an economical evaluation of a conventional transformers project vs. self-protected project
TRANSFORMER SIZES COMPARED ARE DIFFERENT !!
CONVENTIONAL
SELF - PROTECTED
kVA RATING = X
kVA RATING = X/2
HJ International Latin America, Inc.

49. HJ International Latin America, Inc.
Introducing Self Protecting Philosophy can help to simplify and to reduce costs of Distribution Circuits
No use of cross arms for arresters
No use of cross arms for Cut-outs
Use of line spacers & wildlife guards
No LV fuse holders
HJ International Latin America, Inc.

50. HJ International Latin America, Inc.
LOAD HARMONICS
LOAD HARMONICS CAUSING OVER HEATING INSIDE THE TRANSFORMERS WILL ALSO CAUSE OVER HEATING OF THE BREAKER’S BIMETALIC, TRIPPING IT.
HJ International Latin America, Inc.

51. HJ International Latin America, Inc.
Breaker Losses
ANY COST ANALYSIS OF THE BREAKER LOSSES BASED ON THE ACTUAL LOAD CURVE WILL SHOW THAT IT IS TOO LOW PER YEAR MAKING THE LOW VOLTAGE BREAKER THE MOST ECONOMICAL AND FLEXIBLE ALTERNATIVE TO PROTECT THE TRANSFORMER
HJ International Latin America, Inc.

52. Light & Breaker trip temperatures can be selected based on the kWh demand curve
LOAD CURVE
kWh DEMAND CURVE
TEMPERATURE PROFIL
TRIP TEMPERATURES DETERMINATION
HJ International Latin America, Inc.

53. HJ International Latin America, Inc.
SELF PROTECTION APPLICATION COVERS SMALL DISTRIBUTION TRANSFORMERS (UP TO 500kVA) THAT NORMALLY DON’T USE THERMOMETERS OR LIQUID LEVEL GAUGES
BREAKER’S BIMETALIC ACTS LIKE A TEMPERATURE DETECTOR WITH ALARM & TRIP FEATURES WHEN INTERNAL TRANSFORMER’S TEMPERATURES REACH DANGEROUS PREDETERMINED LEVELS
BREAKER’S BIMETALIC ACTS ALSO LIKE A LOW OIL LEVEL DETECTOR WITH ALARM & TRIP FEATURES WHEN INTERNAL OIL REACHES LEVELS WHERE THE BIMETAL GET NOT OIL IMMERSED
HJ International Latin America, Inc.

54. Expected life of the transformer oil
DUE TO THE OPERATING TEMPERATURE CONTROL, SELF-PROTECTED TRANSFORMERS MAKE OIL LIFE LONGER THAN CONVENTIONAL
POSSIBLE OIL DETERIORATION CAUSED BY UNDER-OIL ARCING IS FAR COMPENSATED BY THE LOW OIL OPERATING TEMPERATURE DURING THE LIFE OF SELF-PROTECTED TRANSFORMERS
NUMBER OF BREAKER OPERATIONS DURING TRANSFORMER’S LIFE IS MINIMIZED BY MAKING A RIGHT USE OF THE SIGNAL LIGHT
HJ International Latin America, Inc.

55. Customized thermal protection based on heat run test
THERE IS A DIFFERENT CALIBRATION AVAILABLE EVEN FOR THE SAME kVA RATING
TEMPERATURE RANGE FOR TRIP CALIBRATION SIGNAL LIGHT BREAKER
OTHER PROTECTING DEVICES LIKE FUSES OR COOPER MAGNEX ARE NOT SO FLEXIBLE
HJ International Latin America, Inc.

56. COMPARISON BETWEEN SECONDARY BREAKER VS PRIMARY MAGNEX INTERRUPTER
HJ International Latin America, Inc.

57. HJ International Latin America, Inc.
COMPARISON BETWEEN SECONDARY BREAKER VS PRIMARY MAGNEX INTERRUPTER …CONTINUED...
HJ International Latin America, Inc.

58. HJ International Latin America, Inc.
COMPARISON BETWEEN SECONDARY BREAKER VS PRIMARY MAGNEX INTERRUPTER …CONTINUED
HJ International Latin America, Inc.

59. HJ International Latin America, Inc.
SUMMARY
We have seen during this presentation:
Over capacity problem of the Distribution Systems & causes
Our proposal of solution
Effect of the over capacity & its solution on losses and failures
What is and how works the self protected transformers concept
Principles of Self Protection philosophy & performance of a self protected unit in the distribution circuits
How to begin a change process to successfully introduce the Self Protection philosophy without mistakes
HJ International Latin America, Inc.

60. HJ International Latin America, Inc.
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HJ International Latin America, Inc.