International Telecommunication Union
ITU-T Study Group 5
The need for special
requirements
Tetsuya Tominaga
Technical Session on Home Networks
Geneva, 29/04/2011
AC mains plugs in global
ITU-T
Study Group 05
o There are many plugs in the world
o There is no earth terminal in Japanese
type
JAPANESE TYPE
Technical Session - Home Networks - Geneva
Japanese customer premises AC power
o
o
ITU-T
Study Group 05
o
o
o
Voltage: 100 V rms
Frequency:
• 50 Hz Eastern Japan
• 60 Hz Western Japan
Configuration: TT
Each PE has each grounding rod
Technical Session - Home Networks - Geneva
Smart House is “Connected House”
ITU-T
Many kinds of equipment will be connected each other
under the TT system.
Study Group 05
Optic
Fiber
Smart Meter
SPD：Surge Protective Device
7/3/2011
TTC WorkShop
4
Bad installation and insufficient
resistibility
ITU-T
Good installation and Adequate resistibility are needed.
Study Group 05
Optic
Fiber
Smart Meter
SPD：Surge Protective Device
7/3/2011
TTC WorkShop
5
Philosophy of protection
Good installation and Adequate resistibility of equipment
ITU-T
Classification of
interface (K.75)
Adequate Resistibility
(K.21,K.44,K.66,K.71,K.hnwr)
Study Group 05
Optic
Fiber
SPD
SPD
SPD
Additional Protection (K.66)
Good Bonding (K.66)
Who knows K.66?
Is Japanese type grounding configuration special?
7/3/2011
TTC WorkShop
SPD：Surge Protective Device
6
Selection for Required resistibility
(K.hnwr/Draft)
Figure 1/K.hnwr - Flowchart for determining required level of resistibility
Identify the equipment and the
number and type of ports
ITU-T
Determine the
power induction limits
Study Group 05
When the bonding
configuration is
not along with
K.66
Are there unique
problems requiring
high isolation values?
Bad bonding
configuration
(K.66 For example,
the bonding wire
length >1.5m )
Yes
No
Does the equipment
have more than one
port type?
Yes
No
Are the power
induction limits >
600 V?
Yes
No
“Basic”
“Enhanced
”
5.2 Resistibility
Recommendation K.21 has two levels of
resistibility “basic” and “enhanced”.
Specification EN 50468:2009 gives advice
on the selection of “basic” and
“enhanced”. EN 50468:2009 advises:
For equipment having only external
telecommunication ports the resistibility
requirements are defined in ITU-T K.21
“Basic level”.
For equipment having additional
connections to networks e.g. power
networks, the test levels are defined in
ITU-T K.21 “Enhanced level”
The required level of resistibility can be
determined in Figure 1/K.hnw.
Information on “Special requirements”
is contained in K.44.
“Special”
Figure 1/K.hnwr - Flowchart for determining required level of resistibility
7/3/2011
TTC WorkShop
7
Proposal: Special Resistibility
(K.44, K.66,K.hnwr)
ITU-T
Study Group 05
TEST
The special level is already described in K.44 and K.66.
The external port is optical fibre now.
So, All telecom. Ports are “Internal”
The proposal is adequate Internal port test levels
Telecom
Telecom Telecom
Telecom
Mains
Mains
Mains municati Internal
municati municati
municati
Internal Internal
power
power
power – on line – tel. Port –
Internal
on line
on line
on line –
tel. Port
Ether
longitudi transvers
Internal
Mains
Internal
USB Port
longitudi transvers
Internal
(L1-L2)
Port
nal
e
port
power tel. Port
nal
e
port
line
4 kV
13 kV
Combin
Lightnin
10 kV 10 kV
10 kV 10/700 10 kV
ation
13 kV
4 kV
13 kV
g Surge
combina combina
combina 10 kV combina Current
10/700 10/700
10/700
limit
Test
tion
tion
tion combina tion
resistor =
tion
50W
Table II.6-1/K.44 – Resistibility and safety requirements
of customer premises equipment powered by mains
power
Proposal
Technical Session - Home Networks - Geneva
10kV
??
6 kV
??
Under
Study
Coax.
Port
6.42kA
10/350
K.75
For SPD
Concideration
Coordination of “protecters” and “Safety and Lightning
protection” are important.
ITU-T
Study Group 05
Safety = Breaking Fuse
Minimize of Damage ratio = No Breaking Fuse
The impedance is need
for coordination
FUSE
between SPDs
SPD2
V2
SPD1
o Resistibility of inherent IC’s
or circuit is becoming
smaller, so it becomes more
difficult to prevent the
damage.
V0
o No Earth is Un safe?
V1
Coordination of protection
Un safe method
Class II without earthed SPDs
Safe method
Class II with earthed SPDs
A
A
N
N
E
E
Safety and lightning Protection in no earth
7/3/2011
TTC WorkShop
9
Bypass circuit and Safety
standard
ITU-T
Study Group 05
o Conflict between Safety standards (e.g. IEC 60950) and
Lightning protection (Recommendation K.66 and so on).
• Bypass circuits between AC mains and telecom ports described
in K.66 should be permitted in any case to protect
telecommunication equipments against overvoltages.
• The protector operate voltage would be higher than the
insulation test voltage. Unfortunately the safety standards, e.g.
IEC 60950, do not allow voltage limiters to bridge
supplementary insulation, double insulation or reinforced
insulation.
TD566 is describe in detail, please read them.
Technical Session - Home Networks - Geneva
Conclusion
ITU-T
Study Group 05
7/3/2011
o If we are to prevent damage to HNW
equipment we need:
• Adequate resistibility of equipment
• Special resistibility of equipment, when
the equipment can not be controlled the
installation environment.
• Correct classification and use of ports
• Good installation practices
• Correct earthing and bonding
• Protection for external and internal
ports as necessary.
TTC WorkShop
11