Mod_06_18 – PMEA Theoretically there should always be at least one Bid Offer Acceptance (BOA) Quantity which is unflagged and is therefore the Marginal Energy Action; However this does not account for other aspects of pricing which could remove the unflagged action from the process on rare occasions, such as the De Minimis Acceptance Threshold (DMAT) parameter which excludes BOAs with sufficiently small quantities; In the current drafting the process for calculating the Marginal Energy Action Price has no stated outcome for what should happen if there is no unflagged action, therefore the process “fails” and the Market Back Up Price for the whole half-hour should be the result; However this removes all of the information which is present in the flagged actions of the cost of balancing in a period, including Imbalance Pricing Periods where the process ran correctly; Also the current process for when there is an overly large proportion of actions flagged than required to meet the NIV is to untag some of those actions in the NIV Tagging stage: this proposal is to extend that process to the scenario when all actions are flagged

Mod_06_18 – PMEA This proposal would be to implement a pure NIV Tagging approach in situations where there are no unflagged actions, by unflagging the volume of actions required to meet the NIV, keeping the most expensive actions tagged out: This is expanding the current treatment of the situation where there are too many flagged actions, where some actions become untagged during the NIV Tagging process. Setting PMEA to PCAP or PFLOOR is a means of allowing the process to continue and carry out pure NIV Tagging in a way which means PCAP and PFLOOR will not impact the final result: The Replacement Bid Offer Price stage of the process will ensure that this PMEA will not continue in the process unless there actually was a BOA at the price of PCAP or PFLOOR. The other part of this proposal is a simple moving of a parenthesis to ensure that the meaning of the drafting unambiguously matches the intended design: Intention is for PMEA to be the marginal (highest/lowest) priced BOA whose associated Imbalance Price Flag is equal to one, however the current wording does not make this clear.