1. Voltage Regulators

2. Outline Regulator Function & Purpose What is inside Neutral Position
Nameplate
Bypassing
Basic Control Settings
What is the function of a voltage regulator? To monitor voltage and maintain it within a preset range.
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3. Voltage Regulator Function
What is the function of a voltage regulator?
The basic function of a voltage regulator is to monitor voltage and maintain it within a preset range.
What is the function of a voltage regulator? To monitor voltage and maintain it within a preset range.

4. VLD = Voltage drop due to line losses End of line
TRANS-
FORMER
VLD = Voltage drop due to line losses
End of line
VLD
Voltage
Distance

5. LOAD CURRENT VS
TIME OF DAY
CURRENT
12am
6am
12pm
6pm
TIME OF DAY

6. How to Reduce Voltage Drop
Change taps on distribution transformers
Change taps of substation transformer
Reconfigure system
Install larger conductor
Increase system voltage
Install line capacitors
INSTALL LINE REGULATORS
Notes or Observations
_______________________________________________________________

7. Voltage Regulators Purposes
Primary Purpose
Provide regulated voltage to meet power quality criteria
Secondary Purposes
Increase revenue
Peak shaving
Conservation voltage reduction
Metering point
Notes or Observations
_______________________________________________________________

8. Power Quality What is the right voltage level?
±10% (132 to 108) Outage
±5% (126 to 114) Guideline
±2.5% (123 to 117) Customer expectation
Notes or Observations
_______________________________________________________________

9. Series
Winding
Shunt
Winding
ANSI TYPE B

10. Conventional two-winding transformer+ +
Vp = 1000V
Vs = 100V - -
10:1

11. Step-Up Autotransformer+ +
Vs = 1100V
Vp = 1000V - -

12. Step-Down Autotransformer+ +
Vp = 1000V - -
Vs = 900V

13. Step Regulator + N + 1 2 3 4 5 6 7 - 8 -

14. Step Regulator with Revsersing Switch+ N + 1 2 3 4 5 6 7 - 8 -

15. 1.25% N 1 2 3 4 5 6 7 8
Non-Bridging

16. 1.25% N 1 2 3 4 5 6 7 8
Bridging

17. TYPE B REGULATOR REVERSING SWITCH 1.25% SERIES WINDING L S N 1 2 3 4 56 7 8
CURRENT
X-FORMER
CONTROL
SHUNT
WINDING
TYPE B
REGULATOR
CONTROL
WINDING SL

18. Step Voltage Regulator Components
The step regulator evolved as less costly device that could still maintain voltage within acceptable limits. Like the induction regulator, the step regulator has a shunt winding and a series winding. However, instead of having a moveable winding to induce a raise/lower voltage in the series winding, the shunt winding of a step regulator constantly induces a voltage in the series winding in the opposite direction, it utilizes a motor driven tap changer to change the regulator’s output, and employs a reversing switch that connects the series winding in the direction necessary to raise or lower the voltage. (Identify the bridging reactor for later reference.) Also note that the regulator shown here has only 4 taps, hence only 8 raise positions and 8 lower positions. The entire range of the regulator is raise or lower 10%. Each tap is worth 180 volts if connected to a 7200 volt source. Each step is therefore worth 90 volts.
SHUNT
WINDING

19. Voltage Regulator Connection in a Single-Phase Circuit
Notes or Observations
_______________________________________________________________

20. Regulator Neutral
The regulator shown here is in the neutral position. The tap changer is at the neutral tap which has the series winding isolated from the load end and the reversing switch is open, isolating the winding from the source end. (Point this out on the slide.)
720V

21. Regulator Raise Operation
When the regulator is called upon by it’s controller to raise the voltage, the motor starts moving the tap changer (clockwise as shown). This action also closes the reversing switch to connect the series winding in such a direction that the source voltage is added to the induced voltage. Note here that the tap changer has 2 contacts. This is necessary to keep from opening the circuit during a tap change. This would appear to short out a section of the series winding, and indeed this would be the case if not for the bridging reactor. The bridging reactor is a coil, connected across the leads of the tap changer and prevents the series winding from shorting out. This coil is center tapped and so connected to the load. As we see in the slide, the regulator has moved 1 step; 1 contact is on the #4 tap and the other is on the neutral tap. This is known as bridging. The #4 tap itself is worth 180 volts and that amount of voltage is place across the bridging reactor. With the load connected to the reactor’s center tap, only half of the #4 tap’s 180 volts are added to the source voltage.

22. Regulator Raise Operation
If a further voltage increase is needed, the tap changer continues and makes another step. Both of the tap changer contacts are now on the #4 tap. Here, the bridging reactor sees no difference in voltage and the load current merely flows through both sides of the reactor with the full 180 additional volts contributed by the #4 tap.

23. And So It Goes
And so it goes, on and on, picking up more of the series winding, until the desired voltage is reached or the regulator maxes out.

24. Picking up More Series Winding
And so it goes, on and on, picking up more of the series winding, until the desired voltage is reached or the regulator maxes out.

25. Full Raise
And so it goes, on and on, picking up more of the series winding, until the desired voltage is reached or the regulator maxes out.

26. To Lower Voltage
If the regulator is called on to lower the voltage, the tap changer moves in the opposite direction to neutral. (Show tap changer on neutral tap and reversing switch open.

27. Regulator Lower Operation
7110V
Note now that the reversing switch has now connected the source to the series winding in such a fashion that the source voltage and series are bucking each other. The tap changer has moved 1 step, bridging #1 tap and neutral, lowering regulator output by 90 volts. This continues on and on, one step at a time until the required voltage is reached or the tap changer reaches it’s limit.

30. Switching Checklist Putting Regulator In Service
Check potential transformer settings.

31. Back Panel with Modular Terminals & Switches
RCT2
RCT1
V6, V1, & C switches
TB2
TB1
Optional FO-RS232 Board

32. BYPASSING Regulator Hazards
The most hazardous thing to do with a regulator; BYPASSING
BYPASSING

33. ABSOLUTELY, POSITIVELY
A voltage regulator MUST be in the neutral position in order to “bypass” it while it is energized.
A line/service technician must know how to operate the controls in order to maneuver the regulator into the neutral position.
(READ SLIDE!)

34. AEP Safety Manual E 9.01 States: “Voltage regulators shall be placed in the neutral position, verified by two approved methods to be in the neutral and the control circuit made inoperative before they are bypassed.
AEP Safety Manual (Revised July 15th, 2002) E 9.01 states; “Voltage regulators shall be placed in the neutral position, verified by two approved methods to be in the neutral and the control circuit made inoperative before they are bypassed.” Opinions from staff in AEP Safety are that in order to meet the requirements of “tested”, the Hastings RND will be used.

35. Voltage Regulator Neutral Position
Mechanical Indication: Position indicator
Position indicator. Center position of the indicating needle (or zero) is the neutral position. Clockwise from neutral is raise positions, counter-clockwise is lower positions. Point out also the range limit controls on the side of the enclosure.

36. Voltage Regulator Neutral Position
Electrical Indication: Neutral light
Indicating lights. The neutral light is an electrical indication of neutral position.

37. Hastings Neutral Detector
Is a specifically designed voltmeter installed on a hot stick that measures the difference in voltage between the source and load conductors.
This device is a specifically designed voltmeter with a digital readout that measures the voltage difference between the source and load sides of the regulator. It is used from the end of a hot stick and measures the difference in voltage between the source and load sides of the regulator. A regulator in the neutral position will result in a reading of “0” (zero) or near zero on the display.

38. Low impedance bypass loop
Here’s what happens if a regulator is bypassed when not in neutral. You are trying to connect 2 conductors at different potential and that portion of the series winding being used shorts out. The shorted portion of the circuit is shown is green. When only a portion of the coil is connected, there is little impedance (a combination of factors that opposes current flow) that would tend to limit fault current. The fault current builds up rapidly. Tests at GE labs have observed currents of over 300 times the series winding’s rated capacity. The winding obviously cannot carry that much current and is destroyed. If you’re lucky, you’ll only burn the winding up. However, this internal damage has the potential for disastrous results including case destruction, switches welding shut, spectacular electrical displays, massive oil spills… The more windings in use (or the further the regulator is off neutral), the more impedance available, hence a greater restriction to fault current. Therefore, the worst possible tap position for an attempted regulator bypass is 1 step to either side of neutral.

39. Regulator Bypass Switches
Non-sequenced Switch

40. Regulator Bypass Switches
Kearney (sequenced switch)

41. Switching Checklist Taking Regulator Out Of Service
Check position of regulator.
Place regulator in the neutral position.
Turn control to “off”.
Verify neutral position.
Disable control panel power source.
Test regulator to be in neutral.
Operate bypass switch as required depending on type of switch.

42. Bypassing - Remove Procedure Regulator Connected Line-to-Ground (GY)
Source
Load
Phase A B
S-DIS
L-DIS S L
Start 1 2 3 B O C
S-Dis
L-Dis SL
Neutral
Step 1 is Critical Operation.

43. Bypassing - Install Procedure Regulator Connected Line-to-Ground (GY)
Source
Load
Phase A B
L-DIS
S-DIS
Start 1 2 3 B C O
S-Dis
L-Dis S L SL
Neutral
Step 2 is Critical Operation.

44. Switching Checklist Putting Regulator In Service
Check potential transformer settings.
Check regulator in neutral and off position.
Check power source disabled.
Test regulator to be in neutral.
Operate bypass switch as required.
Enable control panel power circuit.
Place regulator control to “automatic”.

45. When should a regulator be de-energized before bypassing?
De-energizing
When should a regulator be de-energized before bypassing?
The regulator is inoperative and cannot be returned to the neutral position.
Sometimes, regulators are inoperative and they just can’t be brought back to neutral. In these cases, there is simply no choice except to de-energize the regulator and take it out of service. The unit may have to be changed out or it may be possible to make repairs in the field. In either case, the regulator can be operated by an external low voltage power source and be placed in neutral prior to placing it back in service.
The regulator cannot be insured to be in the neutral position.

46. As a lineman who operates regulators, here are some of the major external components with which you must be familiar. On the top left is shown a typical mechanical position indicator. The yellow needle indicates the position that the regulator is currently in. The silver hands on either side of the yellow needle are the “drag hands” which are shoved by the yellow position indicating needle and show the maximum raise and maximum lower levels that the regulator has operated to since they were last reset. Most drag hands are electrically reset by pressing a button in the regulator control. A few old regulators have drag hands which are reset by physically moving the hands back against the position indicating needle.
On the bottom left is shown a position indicator housing and a black knob on the side. This is the range limit switch for the lower function. An identical switch exists on the opposite side for the raise limit. It is sometimes desirable to limit the range to which a regulator can operate. These switches are used for the desired settings.
The photo on the right is one of a typical older style regulator control. These are being replaced across the AEP system with microprocessor controls but there are a lot of these still around. (Point out control knobs, test terminals, drag hand reset, neutral light, counter, etc…)

47. Another regulator unit. (Point out similarities.)

48. BASIC CONTROL SETTINGS
Set Voltage
Bandwidth
Time Delay
Control operating mode
Reverse sensing mode
Configuration
System voltage (nominal)
P.T. & C.T. ratios
Line drop compensation
Notes and Observations:
_________________________________________________________

49. Set Voltage
The voltage level (in 120V base) to which the control will regulate
Settable for both forward & reverse power flow
Forward set voltage = Function code (FC) 1
Reverse set voltage = FC 51
Default values are 120.0V
Notes and Observations:
_________________________________________________________

50. Bandwidth
The total voltage range around the set voltage which the control will consider acceptable
Acceptable voltage range defined as: Range = SV +/- 1/2 BW
Notes and Observations:
_________________________________________________________

51. Time Delay
The number of seconds the control waits, from the start of an out-of-band condition, before initiating a tap change
Typical values are 30 through 90 sec….
Notes and Observations:
_________________________________________________________

52. Time Delay & Cascading Regulators
SVR
TD = 45 SEC
SVR
TD = 75 SEC
3-phase
LTC
transformer
TD = 30 SEC
SVR
TD = 45 SEC
SVR
TD = 60 SEC
SVR
TD = 75 SEC
Notes or Observations
_______________________________________________________________
SVR
TD = 45 SEC
Rule 1: Each succeeding regulator in series down line from the
source requires a longer time delay
Rule 2: The minimum time delay from one regulator to the next
in cascade is 15 seconds

53. Control Operating Mode
Defines for the control how to respond to out-of-band conditions
Options
Sequential (FC 42 = 0)
Time integrating (FC 42 = 1)
Voltage averaging (FC 42 = 2)
Notes and Observations:
_________________________________________________________

54. SEQUENTIAL c=30 c=0 c=10 c=0 2 sec delays (horizontal) 30 sec. out-
of-band
121.0
UBE
in-band
120.0 SV
time
119.0
LBE
tap changes
(vertical)
10 sec. out-
of-band
5 sec .
in-band
counter
resets to
zero
Given:
SV=120.0
BW=2.0
TD=30

55. TIME INTEGRATING 2 sec delays (horizontal) c=30 c=0 c=10 c=4.5
out-of-band
UBE
121.0
in-band
120.0 SV
time
LBE
119.0
tap changes
(vertical)
10 sec. out-
of-band
5 sec. in-band;
counter decremented
1.1/sec in-band
Given:
SV=120.0
BW=2.0
TD=30

56. VOLTAGE AVERAGING average voltage tap changes w/no 2 sec.
delay between
taps
c=30
c=0
out-of band
121.0
UBE
in-band SV
120.0
time
LBE
119.0
10 sec. out-
of-band
5 sec.
in-band
Given:
SV=120.0
BW=2.0
TD=30

57. Reverse Sensing Mode
Reverse sensing mode defines for control what RPF (Reverse Power Flow) is and how it is to react
Options are locked forward, locked reverse, reverse idle, bi-directional, neutral idle, and co-generation
Notes and Observations:
_________________________________________________________

58. Configuration
Defines for the control how the regulator is connected in the power system
Necessary for proper phase relationships
Configuration = FC 41
Options
Wye (FC 41 = 0)
Delta lag (FC 41 = 1)
Delta lead (FC 41 = 2)
Notes and Observations:
_________________________________________________________

59. System Line Voltage
The nominal system voltage at which the regulator is to operate
System line voltage = FC 43
Obtain value from regulator nameplate
Notes and Observations:
_________________________________________________________

60. Overall P.T. Ratio
Ratio of system line voltage to voltage sensed by the control when in neutral position
Overall PT ratio = FC 44
Obtain value from nameplate based on selected system line voltage
Notes and Observations:
_________________________________________________________

61. Nameplate System Voltages 14400 Volts, 60 Hz
TAP
CONTROL
INTERNAL
R.C.T.
TEST
OVERALL IN
LOAD
WDG.TAP
P.T.
TAP
TERMINAL
POT.
USE
VOLTS
(TANK)
RATIO
(CONTROL)
VOLTAGE
RATIO
14400 E1
120:1
120
120
120:1
13800 E1
120:1
115
120
115:1
13200 E1
120:1
110
120
110:1
Notes and Observations:
_________________________________________________________
12000 E1
120:1
104
115
104:1
7970 E2
60:1
133
120
66.5:1
7620 E2
60:1
127
120
63.5:1
7200 E2
60:1
120
120
60:1
6900 E2
60:1
115
120
57.5:1
Note: The ratios may be different for each load current rating

62. Line Drop Compensation
VDROP L S I R X
FC 9 SL
VCOMP
VIN
Load
Center
VOUT
FC 7
FC 8
FC 6
Notes and Observations:
_________________________________________________________
VCOMP = VOUT - VDROP R VR
FC 4 X VX
FC 5