Download DC System Failure Modes Part 1

Technical Panel Session. Sunday January 11, 2015.
DC System Failure Modes
Chair
J. Allen Byrne
Technical Support and Services Manager
Interstate PowerCare
A Division of Interstate Batteries
IEEE PES SBC Winter Meeting.
January 11 – 15, 2014. New Orleans, LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
J. Allen Byrne
Interstate PowerCare
Some Background
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
Curtis Ashton. Century Link
.
Representing the Telco Industry.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
Kurt Uhlir
Standby Power System Consultants, Inc.
J. Allen Byrne
Representing the Utilities Industry
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
George Pedersen
Btech
Representing the Monitoring Industry
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
Rob. Schmitt
Representing the Battery Manufacturers.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
Some Background.
J. Allen Byrne
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Technical Panel Session. Sunday January 11, 2014
DC System Failure Modes
Notes.
At the Summer Meeting in Newport, RI, The SBC selected
the topic “DC System Failure Modes” to be presented as a
Sunday Tutorial Session for the Winter Meeting.
The first question was how does one define DC Systems?
This tutorial will focus on those system where the DC
output powers the load.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Why DC Power Systems
The telecommunications network uses and has
always used a 48-volt DC power as its standard.
Pioneering telecom engineers, faced with the need
for guaranteeing high reliability of telephony
operations, knew that DC power was the easiest
and most efficient means of delivering reliable
power.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Why DC Power Systems
 There is only one stage of power conversion,
AC to DC.
 It is easy to electrically parallel the rectifiers
for scalability and redundancy.
 It is easy to put battery reserve into the system.
 48 volts was chosen because it was a safe low
working voltage (below 50 volts. And could
accommodate 24 x 2 volt batteries.
 Typically, the power systems rely on multiple
rectifiers operating in a parallel redundant
configuration that allows redundancy and
scalability
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Why DC Power Systems
 The “wire-line” telecom industry uses negative
48 volts.
 However, the “wireless” cellular telecom
industry mainly uses positive 24 volts.
 The difference is because of the way the two
industries were derived.
 The cellular systems are slowly migrating
towards 48 volts.
 The microwave industry tends to use 48 volts.
 The utility industries use both 24 and 48 volt and
also 120 volts DC.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
SPD
Inverter
Eng/Gen
Utility
AC
ATS
Utility Infrastructure
AC Input
Rectifiers
Batteries
DC Distribution
Protected AC
Loads
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Automatic Transfer Switch.
 Allows automatic switching from a
primary power source to a secondary
source, usually an engine generator.
 Switches back to prime source on
power restoration.
 Can incorporate manual and preprogrammed switching.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Simplified drawing of ATS
Typical in Wireless Shelter.
EGS
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Typical ATS installation in engine/generator shelter.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Surge Protection Devices.
 Power surges can destroy electrical
equipment.
 Surge protection devices can mitigate the
damage caused by surges and electrical
spikes.
 Most operate by diverting the surge to
ground.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Rectifier/Chargers
Rectifier/Chargers take an AC input and Rectify it to DC while at
the same time providing a regulated and filtered DC input for the
load, power an inverter and also float charge a battery.
EGS
ATS
Rectifiers N+1 Redundant
Rectifier/chargers are usually configured in a parallel configuration with
one or more additional rectifiers that are required for the load and
battery charging in order to provide redundancy. (N + 1 configuration).
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
What a Rectifier/Charger does:

Rectifies AC to DC

Charges the battery.

Provides regulated and filtered DC power to the load.

Can operate on its own or in parallel.

Can load share.

Acts as a power supply.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Different Types of Rectifier/Charger Design
 Silicone Controlled Rectifier. (SCR)
 Controlled Ferroresonant Rectifier (CFR)
 Switching Mode Rectifier (SMR)
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Different Types of Rectifier/Chargers
Silicone Controlled Rectifier. (SCR)
 Uses SCR’s along with conventional


transformers to regulate the charger output.
The SCR’s provide precise control and can be
easily be interfaced by a microprocessor.
They work well with all types of batteries.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Different Types of Rectifier/Chargers
Controlled Ferroresonant Charger
 Employs a ferroresonant transformer to regulate



one in parallel with a capacitor and the core is
driven into saturation.
The charger output is derived from the saturated winding an is
relatively independent of the input.
The circuit is relatively simple but they lack sophisticated
control circuitry.
They are less suitable for charging VRLA batteries.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Different Types of Rectifier/Chargers
Switch Mode Rectifiers
 Use fully controllable switching power devices such



as IGBT’s and MOSFET’s.
They operate at frequencies in the MHz range.
They allow precise control of the charger output.
They work well with all types of batteries.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Utility Chargers
Usually SCR
Trending towards SMR
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Rectifier/Charger Type Comparison
FEATURE
CFR
SCR
SMR
Efficiency 50% Load
78%
81%
85%
Efficiency 100% Load
80%
87%
92%
Response
Very slow
Medium
Very Fast
Ruggedness
Excellent
Excellent
Good
Complexity
Low
Medium
High
Control
Low
Medium
High
Noise
High
Medium
Low
Weight/Size
Heavy/Large
Heavy/Large
Light/Small
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Rectifier/Charger Type Comparison
FEATURE
CFR
SCR
SMR
Current Limit
125%
120%
110%
O/P Regulation
1%
0.5%
0.5%
I/P Surge Immunity
Poor
Excellent
Excellent
O/P Ripple P-P
500 mV
100 mV
100 mV
EMI Emission
Poor
Excellent
Good
Power Factor 100% load
0.7
0.99
0.97
Power Quality
Very Good
Poor
Vey Good
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Modern Switch-Mode Rectifiers. Typical Main Features
 Wide input voltage range.
 Wide output voltage range
 Choice of cooling. Fan cooled, convection cooled
 High reliability. >1,000,000 hours
 Good regulation over input and output range.
 Low noise radiation. Both EMI and RFI.
 Power factor corrected.
 Hot plug for easy expansion and N+1redundancy
 High power density
 High efficiency
 Wide operating temperature range
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Industry Drivers for Switch Mode Rectifiers
 High Power Density
 Typically 10 Watts per cubic inch or less
 Low weight
 Less space needed to accommodate power
equipment. Better use of real estate.
 Easier to install and maintain.
 Wide operating temperature. Typically -40 to +50 °C
 No need for Air Condition in many applications.
 Suits many applications especially outdoor and
remote sites.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
300 Amp Redundant System
CFR compared to SMR
+
=
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Typical DC Power System
Hot Plug?
 Minimal skill needed to change or install products.
 Idiot proof.
 Very low Mean Time to Repair.
 No disturbance to operation of telecom system.
 Totally safe.
 Blind mate rear panel connection.
 Series output diode protection.
 Post mate enable.
IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA