U.S. patent application number 10/330148 was filed with the patent office on 2003-07-17 for environmentally hardened ethernet switch.
Invention is credited to Pozzuoli, Marzio Paride.
Application Number | 20030135601 10/330148 |
Document ID | / |
Family ID | 4171039 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030135601 |
Kind Code |
A1 |
Pozzuoli, Marzio Paride |
July 17, 2003 |
Environmentally hardened ethernet switch
Abstract
A device for hardening an Ethernet switch is disclosed. The
device provides cooling for the switch, and, suppresses electrical
transients and electromagnetic interference, which could affect the
power supply, and data transmission of the Ethernet switch. Using
tills device, the Ethernet switch can be used in harsh industrial
environments, such as those present in power utility
substations.
Inventors: |
Pozzuoli, Marzio Paride;
(Maple, CA) |
Correspondence
Address: |
RICHES, MCKENZIE & HERBERT, LLP
SUITE 1800
2 BLOOR STREET EAST
TORONTO
ON
M4W 3J5
CA
|
Family ID: |
4171039 |
Appl. No.: |
10/330148 |
Filed: |
December 30, 2002 |
Current U.S.
Class: |
709/223 |
Current CPC
Class: |
H04L 49/351 20130101;
G06F 1/20 20130101; G06F 1/182 20130101; H04L 12/10 20130101; H05K
9/0066 20130101; H05K 7/1092 20130101 |
Class at
Publication: |
709/223 |
International
Class: |
G06F 015/173 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 2, 2002 |
CA |
2,366,941 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed is defined as follows:
1. In an Ethernet switch for use in an electrical power utility
substation, a device for cooling the switch comprising: a
thermoelectric cooling element having a first surface for thermally
contacting a component in the Ethernet switch, and, a second
surface for thermally contacting a heat sink, said thermoelectric
cooling element transferring heat from the first surface to the
second surface in response to a current applied to the
thermoelectric cooling element; a control block for applying the
current to the thermoelectric cooling element when the temperature
of the Ethernet switch exceeds a predetermined range.
2. In an Ethernet switch for use in an electrical power utility
substation, a transient suppression device for suppressing
electrical interference to a power supply of the Ethernet switch,
said device comprising: an input connectable to the external power
connector; an output connectable to a power input for the Ethernet
switch; at least one varistor connected in parallel with the input
and output; at least one tranzorb connected in parallel across the
input and output; at least one capacitor connected in parallel with
the input and output.
3. The device as defined in claim 1, wherein the heat sink has a
portion external to the Ethernet switch.
4. The device as defined in claim 1, wherein the heat sink has a
portion external to the electrical power utility substation.
Description
FIELD OF THE INVENTION
[0001] The present invention relates in general to the field of
computer communication networks and specifically to Ethernet
switching hubs (Ethernet Switch) suitable for use in harsh
industrial environments such as those found in electric power
utility substations.
BACKGROUND OF THE INVENTION
[0002] Trends in the electric power utility automation sector,
specifically substation automation, have been driving towards
common communications architecture. The initiative was begun in the
early 1990s driven by the major North American utilities under the
technical auspices of Electric Power Research Institute (EPRI). The
resulting standard that emerged is known as the Utility
Communications Architecture 2.0 (UCA2). At the heart of this
architecture is the substation LAN (Local Area Network) based on
Ethernet. However, one of the major requirements for electronic
devices used in substations as part of a protection and control
system is their ability to operate reliably in harsh environmental
conditions. Harsh environmental conditions include conditions
having both adverse atmospheric conditions and adverse electrical
conditions. Substation environments are much harsher than the
office environments where the overwhelming majority of Ethernet
equipment resides and was designed for.
[0003] It would therefore be desirable for the Ethernet switch,
which forms the backbone of the substation LAN, to be as reliable
and robust as other IEDs (Intelligent Electronic Devices) designed
specifically to operate in harsh substation environments. One such
group of IEDs are protective relays which perform the function of
protecting the power system from fault conditions and other
anomalies. Modern, microprocessor based protective relays are
adhering to the UCA2 standard and providing one or multiple
Ethernet ports ready to connect to suitable Ethernet Switches.
[0004] However, the prior art Ethernet switches do not meet these
standards. In particular, the prior art switches do not adhere to
the ANSI/IEEE C37.90 standard (US)and the IEC-60255 standard
(Europe) which were designed for protective relaying IEDs and other
intelligent devices found in electrical substations. For example,
the prior art devices do not satisfy at least the following
criteria.
[0005] A) Electrical Environment
[0006] 1. Surge Withstand Capability as per ANSI/IEEE C37.90.1
(1989), namely withstanding 2.5 k Voscillatory transients, 4.0 kV
fast transients applied directly across ach output, input and power
supply circuit.
[0007] 2. Surge Immunity as per IEC 61000-4-5 (1995 Level 4)
standards.
[0008] 3. High Frequency Noise Disturbance as per IEC 60255-22-1
(1988 Class III) standards.
[0009] 4. Fast Transient Disturbance as per IEC 60255-22-4 (1992
Class IV) standards, namely withstanding 4 kV, 2.5 kHz applied
directly to the power supply inputs and 4 kV, 2.5 kHz applied
directly to all other inputs.
[0010] 5. Dielectric Withstand as per ANSI/IEEE C37.90-1989 and IEC
60255-5: 1977 standards.
[0011] 6. High Voltage Impulse Test as per IEC 60255-5: 1977
standard.
[0012] 7. Electrostatic Discharge as per IEC 60255-22-2: 1996 Class
4 and Class 3 standards.
[0013] 8. Radiated Radio Frequency Immunity as per IEEE C37.90.2
and IEC 61000-4-3 standards.
[0014] (B) Atmospheric Environment
[0015] 1. Temperature: Cold at -40.degree. C. as per the IEC
60068-2-1 standard and dry heat at 85.degree. C. as per IEC
60068-2-2 standard.
[0016] 2. Temperature Cyclic: -25.degree. C. to +55.degree. C. as
per IEC 60255-6 (1998) standard.
[0017] 3. Relative Humidity: 5 to 95% as per the IEC 60068-2-2
standard.
[0018] Referring now to FIG. 1, an electronic circuit block
diagram, shown generally by reference numeral 10 of a conventional
commercial Ethernet Switch is shown. The circuit 10 consists of an
Ethernet Media Access Controller (MAC) block 1 which typically
provides a plurality of communications ports each adhering to the
Reduced Media Independent Interfaces (RMII) signaling specification
as put forth by the version 1.2 of the RMII Consortium. These RMII
ports interface to a physical layer device 4, referred to as a PHY,
which converts the RMII signals to differential transmit and
receive signal pairs in accordance with the IEEE 802.3 10BaseT and
or 100BaseTX standards. These signals are then noise filtered by
the filter block 5a and electrically isolated via pulse
transformers 5b which also couple the signals to the RJ45 style
connector receptacles 5c which are typical of commercial grade
Ethernet Switches. The RJ45 interface 8 typically accepts TIA/EIA
568 category 5 (CAT-5) unshielded twisted pair copper wire cables.
Power is typically provided by a single power supply block 6 and
cooling of the electronics is also typically provided by a
low-voltage DC powered cooling fan 7 typical of those found in
personal computers.
[0019] The electronic circuit 10 illustrated in FIG. 1 has numerous
shortcomings when used in a utility substation environment. In
particular the switch is susceptible to electrical transients and
electromagnetic interference being coupled into the device via
twisted pair copper cables 8. This is extremely undesirable since
it could result in corruption of real-time mission critical control
messages being transmitted over the network via the switch.
Moreover, actual damage to the switch itself is possible if high
voltage electrical transients are directly coupled into the device
via the copper cables overcoming the limited electrical isolation
(typically 1500V RMS) provided by isolation transformers 5b.
Another point of electrical transient susceptibility in the design
of FIG. 1 is the power supply input 6a. The power supply block 6
must be capable of enduring electrical transients at levels of 2 kV
to 5 kV as specified by the ANSI/IEEE C37.90 and IEC 60255
standards. This is not a requirement for commercial grade Ethernet
Switches and thus the power supply inputs 6a do not provide
suitable transient suppression circuitry. Furthermore, commercial
grade Ethernet switches are not specifically designed to withstand
EMI (Electromagnetic Interference) levels of 35 V/m as specified by
ANSI/IEEE C37.90.2 (1995) which is typical of the substation
environment.
[0020] Accordingly, conventional circuit 10 suffers from the
disadvantage that it is susceptible to electrical transients and
electromagnetic interference at levels which are possible, or even
common, in utility substation environment. The design of FIG. 1 is
also susceptible to mechanical breakdown because of the use of
rotating cooling fan 7 required to cool the electronic components.
Thus the reliability of the Ethernet Switch is determined by the
reliability of the fan which is the only moving mechanical part in
the design and typically has the lowest Mean-Time-Between-Failures
(MTBF) value, such as less than 10,000 Hrs, compared to electronic
components which have MTBF values of greater than 450,000 Hrs. It
would be highly desirable to eliminate the fan block 7 from the
design and improve the reliability of the Ethernet Switch to MTBF
levels similar to those of the IEDs, which would be connected to
it, namely greater than 450,000 Hrs. Furthermore, the typical
operating temperature range of commercial Ethernet Switches having
the circuit 10 shown in FIG. 1, is 0.degree. C. to 40.degree. C.
(ambient) with fan cooling 7. However, the operating temperature
range for devices in the substation environment such as protective
relays is specified by the IEC 60255-6 (1998) standard as
-25.degree. C. to +55.degree. C. Therefore, not only is the circuit
10 of FIG. 1 susceptible to failure, it also does not meet the
requirements of the environmental conditions which are possible, or
even common in utility substation environments.
[0021] Furthermore, because of the mission critical nature of the
application, that being the use of the substation LAN to send
real-time control messages during power system fault conditions,
the availability or "up time" of the Ethernet Switch is critical to
proper operation of the protection and control system. A further
point of susceptibility of the design of FIG. 1 is the power supply
block 6. If the power supply block 6 fails then the Ethernet Switch
fails and is not available to provide the backbone of the LAN
during the critical period of time where the protection and control
system needs to respond in the order 4 to 100 ms. Accordingly,
there is a need in the art for an Ethernet Switch having redundant,
parallel power supply blocks such that if one failed the other
would continue to supply the required regulated power to the
Ethernet Switch without any interruption to its operation.
SUMMARY OF THE INVENTION
[0022] It is the object of the present invention to provide an
improved Ethernet switching hub (Ethernet Switch) which at least
partially overcomes the above-mentioned disadvantages of existing
devices. In addition, it is an object of this invention to provide
an Ethernet Switch that is capable of operating reliably in harsh
industrial environments such as those found in electric power
utility substations.
[0023] In one aspect, the present invention resides in an Ethernet
switch for use in an electrical power utility substation, a device
for cooling the switch comprising: a thermoelectric cooling element
having a first surface for thermally contacting a component in the
Ethernet switch, and, a second surface for thermally contacting a
heat sink, said thermoelectric cooling element transferring heat
from the first surface to the second surface in response to a
current applied to the thermoelectric cooling element; a control
block for applying the current to the thermoelectric cooling
element when the temperature of the Ethernet switch exceeds a
predetermined range.
[0024] In a further aspect, this invention resides in an Ethernet
switch for use in an electrical power utility substation, a
transient suppression device for suppressing electrical
interference to a power supply of the Ethernet switch, said device
comprising: an input connectable to the external power connector;
an output connectable to a power input for the Ethernet switch; at
least one varistor connected in parallel with the input and output;
at least one tranzorb connected in parallel across the input and
output; at least one capacitor connected in parallel with the input
and output.
[0025] One advantage of the present invention is that the circuit
for use in the Ethernet Switch has a high degree of resistance to
electrical transient effects and electromagnetic interferences. In
particular, the circuit provides transient suppression of
electrical signals entering into the power supply. This is
accomplished in a preferred embodiment by using a combination of
transzorbs, metal oxides varistors, and one or more capacitors.
Furthermore, the device provides a conversion block for converting
electrical signals into fiber optic signals and a fiber optical
transmitter/receiver.
[0026] A further advantage of the present invention is that the
circuit provides for thermoelectric cooling. Thermoelectric cooling
increases the reliability of the system and has a much higher MTBF.
Furthermore, the thermoelectric cooling has a larger cooling range
such that, by providing one or more thermoelectric cooling blocks,
the operating temperature range of the entire circuit can be
controlled. Furthermore, in a preferred embodiment, the
thermoelectric cooling can have a heat sink with an extension which
extends outside of the switch and/or the utility station enclosure,
thereby facilitating removal of thermal energy from the enclosure,
and cooling of the entire circuit.
[0027] Further aspects of the invention will become apparent upon
reading the following detailed description and drawings which
illustrate the invention and preferred embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In the drawings, which illustrate embodiments of the
invention:
[0029] FIG. 1 shows a block diagram showing an electric circuit
used in a conventional Ethernet Switch;
[0030] FIG. 2 shows a block diagram showing an electrical circuit
for use in an Ethernet Switch according to one embodiment of the
present invention;
[0031] FIG. 3 shows a schematic diagram of a transient suppression
circuit used in the present invention;
[0032] FIG. 4 shouts a diagram detailing the application of a
Thermoelectric Cooler (TEC) device to an electronic component such
as a microprocessor; and
[0033] FIG. 5 shows a diagram detailing the application of
Thermoelectric Cooler (TEC) device to an electronic component using
an extended heat sink with an external surface.
DETAILED DESCRIPTION OF THE INVENTION
[0034] A preferred embodiment of the present invention and its
advantages can be understood by referring to the present drawings.
In the present drawings, like numerals are used for like
corresponding parts of the accompanying drawings.
[0035] FIG. 2 illustrates an electronic circuit block diagram shown
generally by reference numeral 20, for an Ethernet switch according
to one embodiment of the present invention. The circuit consists of
an Ethernet Media Access Controller (MAC) block 21 with integrated
packet and address memory which provides a plurality of
communications ports each adhering to the RMII (Reduced Media
Independent Interfaces) signaling specification as put forth by the
version 1.2 of the RMII Consortium. Such a block 21 may be
implemented using Marvell 88E6050 or a Galileo GT48350.
[0036] These RMII ports interface to a multi-port physical layer
device 22, referred to as a PHY, which converts the RMII signals to
differential transmit and receive signal pairs in accordance with
the IEEE 802.3 10BaseT and or 100BaseTX standards. The PHY portion
of the circuit can be implemented by an AMD (Advanced Micro
Devices) Am79C875 quad PHY device which is capable of industrial
grade (i.e. -40 to 85.degree. C.) operating temperature.
[0037] For 10 Mbps operation the differential 10BaseT signal pairs
interface to a 10BaseT-to-10BaseFL conversion block 23 which will
convert the 10BaseT differential signal pairs to current drive
signals capable of driving fiber optical LED transmitters 24 and
interfacing to LED fiber optical receivers 24 with outputs as low
as 2 mVp-p and a dynamic range of 55 dB. A Micro Linear ML4669 or
ML6651 may implement the 10BaseT-to-10BaseFL conversion block.
Versions of these components are available which will operate at
industrial grade temperatures.
[0038] The output signals of the 10BaseT-to-10BaseFL conversion
block interface directly to the fiber optical transmitter and
receiver pairs 24. These may be implemented by Agilent Technologies
(Trade Mark) HFBR-2416 and HFBR-1414 receiver and transmitter
component pair. These components are capable of industrial grade
operating temperatures.
[0039] For 100 Mbps operation the PHY devices 22 chosen for the
present embodiment of the invention are capable of directly
interfacing 23b to 100 Mbps fiber optical transceivers 24 with
Pseudo Emitter Coupled Logic (PECL) interfaces that are compliant
with the 100BaseFX version of the IEEE 802.3u standard. The 100
Mbps fiber optical transceivers may be implemented using Agilent
Technologies HFBR-5903 (Trade Mark) or other similar fiber optical
transceiver.
[0040] It should be appreciated that by using a fiber optical
communications medium that the system is no longer susceptible to
electrical transients and electromagnetic interference being
coupled into the device as is the case with the twisted pair copper
cables 8 of FIG. 1.
[0041] Regulated DC voltages, suitable for operating the
electronics, are supplied to the system via dual redundant power
supplies 26. Transient suppression 26a for power supply block #1
26b is provided at the inputs. The same transient suppression 26d
is provided for power supply block #2 26c.
[0042] Referring now to FIG. 3, a detailed schematic diagram of the
transient suppression circuit 26a, 26d used in the present
embodiment of the invention is shown generally by reference numeral
30. Voltage transients entering via the external power connector 31
are filtered back to their source by capacitors 35a, 35b and 35c
which provide a high frequency bypass for both differential and
common mode noise transients. To ensure that transients with high
voltage levels do not exceed the ratings of components such as the
bypass capacitors 35a, 35b and 35c, Transzorbs 33a, 33b, and 33c
and Metal Oxide Varistors (MOVs) 34a, 34b and 34c are used to clamp
both differential and common mode high-voltage transients to
acceptable levels. These components must be rated with high
instantaneous peak-power dissipation capacity. This capacity may be
provided by ST Microelectronic's TRANSIL components or General
Semiconductor's TransZorb components which are capable of
dissipating 400WA to 1.5KW for a period of 1 ms. Suitable MOV
components may be selected from Harris Corporation's ZA series.
[0043] It should be appreciated that the present embodiment of the
invention allows for either Transzorbs 33 or MOVs 34 as a voltage
clamping device depending on what type of failure mode is desired
for these components. Tanszorbs will 33 "fail short" when
parameters are exceeded while MOVs 34 will "fail open" (i.e. open
circuit) when parameters are exceeded. Failing open allows the
system to continue functioning but now leaves the remaining
circuitry in its path unprotected. Failing short will halt the
remainder of the system and typically cause the short circuit fuse
32 to blow thereby isolating the system 30 from any further
damaging transients. The blocking rectifier diode 37 is used to
prevent the application of a reverse polarity voltage source at the
input power connector 1. Capacitor bank 36 provides further
differential mode filtering while common mode choke 38 provides
further common mode filtering of any remnants of noise or harmful
electrical transients which have made it passed the initial bypass
capacitors 36 and the Transzorb 33 or MOV 34 clamping devices.
Suitable values for the capacitor bank 36 capacitors are 680
nF/100V ceramic capacitors manufactured by KEMET. Suitable values
for the common mode choke are 1.2 mH per leg as manufactured by
EPCOS. Preferably, the transient suppression circuit 30 shown in
FIG. 3 is sufficient to pass the electrical transients type tests
as defined by the following standards:
[0044] 1. Surge Withstand Capability as per ANSI/IEEE C37.90.1
(1989) standards.
[0045] 2. Surge Immunity as per IEC 61000-4-5 (1995 Level 4)
standards.
[0046] 3. High Frequency Noise Disturbance as per IEC 60255-22-1
(1988 Class III) standards.
[0047] 4. Fast Transient Disturbance as per IEC 60255-22-4 (1992
Class IV) standards.
[0048] 5. High Voltage Impulse Test as per IEC 60255-5: 1977
standard.
[0049] Referring back to FIG. 2, the outputs of power supply block
#1 26b and power supply block #2 26c are electrically OR-ed via the
OR-ing diodes block 26e. The system 20 has been designed such that
should power supply block #1 fail then all of tie required current
to drive the system will be provided by power supply block #2 and
vice-versa. At the core of each of the power supply blocks is a
high efficiency DC-DC converter such as that provided by Artesyn's
EXB30 which has an operating efficiency of 92% and an operating
temperature of -40 to 85.degree. C. The high efficiency ensures
heat dissipation within the system's enclosure is minimal. It
should be appreciated that the use of dual redundant power supply
blocks in the system 20 improves the system reliability and
availability.
[0050] Cooling for components requiring cooling to maintain their
case temperatures below the manufacturer's recommended operating
limit is accomplished via the thermoelectric cooling block 27. The
cooling block 27 comprises a thermoelectric cooler (TEC) 27a, which
is controlled by an electronic control block 27b, and a temperature
sensor 27c is mounted on the components requiring cooling. The
control block 27b performs the function of measuring the ambient
temperature inside the enclosure of the operating unit via the
temperature sensor 27c, comparing it to predefined limit such as
70.degree. C. and upon the ambient temperature reaching the limit
the control block 27b applies power to the TEC. A control block of
this type can be implemented via a National Semiconductor LM26
Factory Preset Thermostat designed to be mounted on printed circuit
boards for use in microprocessor thermal management systems. The
LM26 integrates the temperature sensor 27c and the measurement and
control block 27b in a package capable of operating over a
temperature range of -55 to 110.degree. C. Beyond this
predetermined range, or other ranges, the control block 27b applies
a current to the TEC 27a.
[0051] FIG. 4 shows a diagram of the application of TEC 43 to an
electronic component such as a microprocessor on a printed circuit
board 45. The TEC itself 43 is mounted in between the component 44
and the heat sink 1 via layers of thermal epoxy 42a, 42b. A DC
current to power to the TEC 43 is delivered via wired leads 46 and
controlled via the TEC control block 27b of FIG. 2. A plurality of
TECs 43 may be applied in the present embodiment of the invention
to components requiring cooling. It should be appreciated that by
eliminating the need for cooling fans and thus rotating mechanical
parts typically found in cooling fans, the reliability and thus the
applicability of the system has been improved.
[0052] FIG. 5 illustrates use of a TEC 53, according to a further
embodiment, to an electronic component using an extended heat sink
51a with an external surface 51b. In some embodiments of the
invention the heat sink 51a is mounted on the TEC 53 via thermal
compound 52a and the external surface 51b extends outside of the
metallic enclosure 57b. It should be appreciated that this heat
sink arrangement allows heat to be conducted outside of the
enclosure 57c and dissipated via convection to the outside ambient
environment.
[0053] Utilizing the present invention will permit data packets to
be transmitted reliably even in harsh. In other words, the
environmentally hardened switch according to the present invention
provides for zero packet loss even in environments in which other
Ethernet switches would not function. This permits the Ethernet
switch of the present invention to function for substantial periods
of time without losing any data, which increases the efficiency and
robustness of the entire system.
[0054] It will be understood that, although various features of the
invention have been described with respect to one or another of the
embodiments of the invention, the various features and embodiments
of the invention may be combined or used in conjunction with other
features and embodiments of the invention as described and
illustrated herein.
[0055] Although this disclosure has described arid illustrated
certain preferred embodiments of the invention, it is to be
understood that the invention is not restricted to these particular
embodiments. Rather, the invention includes all embodiments, which
are functional, electrical or mechanical equivalents of the
specific embodiments and features that have been described and
illustrated herein.
* * * * *