Datasheet

ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569
Rev. B | Page 54 of 152
FAULT DETECTION
The ADE7116/ADE7156/ADE7166/ADE7169 incorporate a
fault detection scheme that warns of fault conditions and allows
the part to continue accurate measurement during a fault event.
(This function is not available in the ADE7566/ ADE7569.) The
ADE7116/ADE7156/ADE7166/ADE7169 do this by continu-
ously monitoring both current inputs (I
PA
and I
PB
). For ease of
understanding, these currents are referred to as phase and
neutral (return) currents. A fault condition is defined when the
difference between I
PA
and I
PB
is greater than 6.25% of the active
channel. If a fault condition is detected and the inactive channel
is larger than the active channel, the ADE7116/ADE7156/
ADE7166/ADE7169 automatically switch current measurement to
the inactive channel. During a fault, the active, reactive, and
apparent power and the I
rms
are generated using the larger of the
two currents. On power-up, I
PA
is the current input selected for
active, reactive, and apparent power and I
rms
calculations.
To prevent a false alarm, averaging is done for the fault
detection, and a fault condition is detected approximately
1 second after the event. Fault detection is automatically
disabled when the voltage signal is less than 0.3% of the full-
scale input range. This eliminates false detection of a fault due
to noise at light loads.
Because the ADE7116/ADE7156/ADE7166/ADE7169 look for
a difference between the voltage signals on I
PA
and I
PB
, it is
important that both current transducers be closely matched.
Channel Selection Indication
The current channel selected for measurement is indicated by
Bit 7 (ICHANNEL) in the ACCMODE register (Address 0x0F).
When this bit is cleared, I
PA
is selected and, when it is set, I
PB
is
selected. The ADE7166/ADE7169 automatically switch from
one channel to the other and report the channel configuration
in the ACCMODE register (Address 0x0F).
The current channel selected for measurement can also be
forced. Setting the SEL_I_CH[1:0] bits in the CALMODE
register (Address 0x3D) selects I
PA
and I
PB
, respectively. When
both bits are cleared or set, the current channel used for
measurement is selected automatically based on the fault
detection.
Fault Indication
The ADE7116/ADE7156/ADE7166/ADE7169 provide an
indication of the part going in or out of a fault condition. The
new fault condition is indicated by the FAULTSIGN flag (Bit 5)
in the Interrupt Status 1 SFR (MIRQSTL, Address 0xDC).
When the FAULTSIGN bit (Bit 6) of the ACCMODE register
(Address 0x0F) is cleared, the FAULTSIGN flag in the Interrupt
Status 1 SFR (MIRQSTL, Address 0xDC) is set when the part is
entering a fault condition or a normal condition.
When the FAULTSIGN bit (Bit 5) is set in the Interrupt Enable
1 SFR (MIRQENL, Address 0xD9), and the FAULTSIGN flag
(Bit 5) in the Interrupt Status 1 SFR (MIRQSTL, Address 0xDC)
is set, the 8052 core has a pending ADE interrupt.
Fault with Active Input Greater Than Inactive Input
If I
PA
is the active current input (that is, being used for billing),
and the voltage signal on I
PB
(the inactive input) falls below
93.75% of I
PA
, and the FAULTSIGN bit (Bit 6) of the ACCMODE
register (Address 0x0F) is cleared, the FAULTSIGN flag (Bit 5)
in the Interrupt Status 1 SFR (MIRQSTL, Address 0xDC) is set.
Both analog inputs are filtered and averaged to prevent false
triggering of this logic output. As a consequence of the filtering,
there is a time delay of approximately 3 seconds on the logic
output after the fault event. The FAULTSIGN flag is indepen-
dent of any activity. Because I
PA
is the active input and it is still
greater than I
PB
, billing is maintained on I
PA
; that is, no swap to
the I
PB
input occurs. I
PA
remains the active input.